LIBRARY 


UNIVERSITY  OF  CALIFORNIA. 


Class 


Masonry  Construction 


A  Guide  to 

APPROVED    AMERICAN  PRACTICE  IN  THE  SELECTION  OF  BUILDING  STONE, 

BRICK,  CEMENT,  AND  OTHER  MASONRY  MATERIALS,  AND  IN  ALL 

BRANCHES    OF   THE    ART  OF  MASONRY  CONSTRUCTION 


By  ALFRED   E.    PHILLIPS,    C.E.,   PH.D. 

Professor  of  Civil  Engineering,  Armour  Institute  of  Technology 

and 
AUSTIN   T.   BYRNE 

Civil  Engineer.     Author  of  "  Highway  Construction," 
"  Materials  and  Workmanship" 


ILLUSTRATED 


CHICAGO 

AMERICAN    SCHOOL   OF   CORRESPONDENCE 
1908 


COPYRIGHT  1907  BY 
AMERICAN  SCHOOL  OF  CORRESPONDENCE 

Entered  at  Stationers'  Hall,  London 
All  Rights  Reserved 


Foreword 


recent  years,  such  marvelous  advances  have  been 
made  in  the  engineering  and  scientific  fields,  and 
so  rapid  has  been  the  evolution  of  mechanical  and 
constructive  processes  and  methods,  that  a  distinct 
need  has  been  created  for  a  series  of  practical 
'working  guides,  of  convenient  size  and  low  cost,  embodying  the 
accumulated  results  of  experience  and  the  most  approved  modern 
practice  along  a  great  variety  of  lines.  To  fill  this  acknowledged 
need,  is  the  special  purpose  of  the  series  of  "handbooks  to  which 
this  volume  belongs. 

C,  In  the  preparation  of  this  series,  it  has  been  the  aim  of  the  pub- 
lishers to  lay  special  stress  on  the  practical  side  of  each  subject, 
as  distinguished  from  mere  theoretical  or  academic  discussion. 
Each  volume  is  written  by  a  well-known  expert  of  acknowledged 
authority  in  his  special  line,  and  is  based  on  a  most  careful  study 
of  practical  needs  and  up-to-date  methods  as  developed  under  the 
conditions  of  actual  practice  in  the  field,  the  shop,  the  mill,  the 
power  house,  the  drafting  room,  the  engine  room,  etc. 

C,  These  volumes  are  especially  adapted  for  purposes  of  self- 
instruction  and  home  study.  The  utmost  care  has  been  used  to 
bring  the  treatment  of  each  subject  within  the  range  of  the  com- 


1 73042 


mon  understanding,  so  that  the  work  will  appeal  not  only  to  the 
technically  trained  expert,  but  also  to  the  beginner  and  the  self- 
taught  practical  man  who  wishes  to  keep  abreast  of  modern 
progress.  The  language  is  simple  and  clear;  heavy  technical  terms 
and  the  formulae  of  the  higher  mathematics  have  been  avoide^d, 
yet  without  sacrificing  any  of  the  requirements  of  practical 
instruction;  the  arrangement  of  matter  is  such  as  to  carry  the 
reader  along  by  easy  steps  to  complete  mastery  of  each  subject; 
frequent  examples  for  practice  are  given,  to  enable  the  reader  to 
test  his  knowledge  and  make  it  a  permanent  possession;  and  the 
illustrations  are  selected  with  the  greatest  care  to  supplement  and 
make  clear  the  references  in  the  text. 

C.  The  method  adopted  in  the  preparation  of  these  volumes  is  that 
which  the  American  School  of  Correspondence  has  developed  and 
employed  so  successfully  for  many  years.  It  is  not  an  experiment, 
but  has  stood  the  severest  of  all  tests — that  of  practical  use — which 
has  demonstrated  it  to  be  the  best  method  yet  devised  for  the 
education  of  the  busy  working  man. 

C,  For  purposes  of  ready  reference  and  timely  information  when 
needed,  it  is  believed  that  this  series  of  handbooks  will  be  found  to 
meet  every  requirement. 


T  a  b  1  e  *  o  .f    Contents 


STRUCTURAL  MATERIALS    .       .       .  -    .       ,       .       .       .       .    Page   1 

Classification  of  Natural  Stones — Requisites  of  Good  Building  Stone — 
Tests  for  Stone  (Absorptive  Power,  Effect  of  Frost,  Atmosphere,  Re- 
sistance to  Crushing-,  etc.) — Preservation  of  Stone — Artificial  Stones — 
Brick  and  Its  Manufacture — Color  of  Bricks — Classification  of  Brick — 
Size  and  Weight  of  Brick — Resistance  to  Crushing  of  Brick — Fire- 
brick— Cementing  Materials — Common  Lime — Hydraulic  Lirne — Rosen- 
dale  or  Natural  Cement — Portland  Cement — Testing  Cement  (Color, 
Weight,  Fineness,  Activity,  Soundness,  Cold  Tests,  Warm- Water  Test, 
Strength,  Briquettes  for  Testing) — Preservation  of  Cements — Slag 
Cement — Pozzuolanas — Roman  Cement — Mortar  (Ordinary,  Cement)  — 
Retempering  Mortar — Freezing  of  Mortar — Concrete — Proportions  of 
Materials — Mixing  and  Laying  Concrete — Asphaltic  Concrete — Clay 
Puddle. 


FOUNDATION  WORK    .       ....       C       ...       .       .       .    Page  39 

Natural  Foundations — Artificial  Foundations — Pile  Foundations — 
Timber  Piles — Iron  and  Steel  Piles — Screw  Piles — Concrete  Piles — 
Pile-Driving — Splicing  Piles — Concrete- Steel  Foundations — Caissons — 
Cofferdams — Sheet  Piles — Cribs — Freezing  Process — Designing  the 
Foundation — Weight  of  Masonry — Bearing  Power  of  Soils — Design 
of  Footings  (Stone,  Timber,  Steel  I-Beams) — Safe  Working  Loads. 


STONEWORK  AND  BRICKWORK    .       ....     ...      ..     .       ."      .    Page  63 

Classification  of  Masonry— Glossary  of  Terms  Used  in  Masonry — 
Dressing  the  Stones — Tools  Used  in  Stonecutting — Glossary  of  Terms 
Used  in  Stonecutting — Finishing  Faces  of  Cut  Stone — Unsquared, 
Squared,  and  Cut  Stones — Ashlar  Masonry — Squared-Stone  Masonry — 
Broken  Ashlar — Rubble  Masonry — Ashlar  Backed  with  Rubble — Gen- 
eral Rules  for  Laying  Masonry  of  Stone;  of  Brick — Face  or  Pressed- 
Brick  Work — Brick  Masonry  Impervious  to  Water — Efflorescence — 
Repair  of  Masonry. 


MASONRY  STRUCTURES       .       .       .       .       .       .f  _     .       .       .    Page  89 

Walls  —  Retaining  Walls  —  Dimensions  and  Proportions  of  Walls  — 
Weep»Holes  —  Surcharged  Walls  —  Kinds  of  Arches  —  Glossary  of  Terms 
Used  in  Arch  Construction  —  Dimensions  of  Arches  —  Flat  Arches  — 
Relieving  Arches  —  Construction  of  Arches  —  Centering  for  Arches  — 
Bridge  Abutments  —  Bridge  Piers  —  Box  Culverts  —  Arch  Culverts  — 
Wing  Walls  —  Concrete  Blocks  —  Concrete-Steel  Masonry. 


INDEX   .        .  '    ..      .        .        .       ,       v      >        .       .        .        .  Page  119 


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N    ^ 


MASONRY  CONSTRUCTION. 

PART  I. 


STRUCTURAL  MATERIALS. 

Classification  of  Natural  Stones.  The  rocks  from  which  the 
stones  for  building  are  selected  are  classified  according  to  (1)  their 
geological  position,  (2)  their  physical  structure,  and  (3)  their  chemical 
composition. 

Geological  Classification.  The  geological  position  of  rocks 
has  but  little  connection  with  their  properties  as  building  materials. 
As  a  general  rule,  the  more  ancient  rocks  are  the  stronger  and  more 
durable;  but  to  this  there  are  many  notable  exceptions.  According 
to  the  usual  geological  classification  rocks  are  divided  into  three 
classes,  viz. : 

Igneous,  of  which  greenstone  (trap),  basalt,  and  lava  are  ex- 
amples. 

Metamorphic,  comprising  granite,  slate,  marble,  etc. 

Sedimentary,  represented  by  sandstones,  limestones,  and  clay. 

Physical  Classification.  With  respect  to  the  structural  char- 
acter of  their  large  masses,  rocks  are  divided  into  two  great  classes: 
(1)  the  unstratified,  (2)  the  stratified,  according  as  they  do  or  do  not 
consist  of  flat  layers. 

The  unstratified  rocks  are  for  the  most  part  composed  of  an 
aggregation  of  crystalline  grains  firmly  cemented  together.  Granite, 
trap,  basalt,  and  lava  are  examples  of  this  class.  All  the  unstratified 
rocks  are  composed  as  it  were  of  blocks  which  separate  from  each 
other  when  the  rock  decays  or  when  struck  violent  blows.  These 
natural  joints  are  termed  the  line  of  cleavage  or  rift,  and  in  all  cutting 
or  quarrying  of  unstratified  rocks  the  work  is  much  facilitated  by 
taking  advantage  of  them. 

The  stratified  rocks  consist  of  a  series  of  parallel  layers,  evidently 
deposited  from  water,  and  originally  horizontal,  although  in  most 
cases  they  have  become  more  or  less  inclined  and  curved  by  the  action 
of  disturbing  forces.  It  is  easier  to  divide  them  at  the  planes  of  divi- 


MASONRY  CONSTRUCTION 


sion  between  these  layers  than  elsewhere.  Besides  its  principal  layers 
or  strata,  a  mass  of  stratified  rock  is  in  general  capable  of  division  into 
thinner  layers;  and,  although  the  surfaces  of  division  of  the  thinner  lay- 
ers are  often  parallel  to  those  of  the  strata,  they  are  also  often  oblique 
or  even  perpendicular  to  them.  This  constitutes  a  laminated  structure. 

Laminated  stones  resist  pressure  more  strongly  in  a  direction 
perpendicular  to  their  laminae  than  parallel  to  them;  they  are  more 
tenacious  in  a  direction  parallel  to  their  lamina?  than  perpendicular 
to  them;  and  they  are  more  durable  with  the  edges  than  with  the 
sides  of  their  laminae  exposed  to  the  weather.  Therefore  in  building 
they  should  be  placed  with  their  laminae  or  "beds"  perpendicular 
to  the  direction  of  greatest  pressure,  and  with  the  edges  of  these 
laminae  at  the  face  of  the  wall. 

Chemical  Classification.  The  stones  used  in  building  are 
divided  into  three  classes,  each  distinguished  by  the  predominant 
mineral  which  forms  the  chief  constituent,  viz. : 

Silicious  stones,  of  which  granite,  gneiss,  and  trap  are  examples, 

Argillaceous  stones,  of  which  clay,  slate,  and  porphyry  are 
examples. 

Calcareous  stones,  represented  by  limestones  and  marbles. 

REQUISITES    FOR   GOOD    BUILDING   STONE. 

The  requisites  for  good  building  stone  are  durability,  strength, 
cheapness,  and  beauty. 

Durability.  The  durability  of  stone  is  a  subject  upon  which 
there  is  very  little  reliable  knowledge.  The  durability  will  depend 
upon  the  chemical  composition,  physical  structure,  and  the  position 
in  which  the  stone  is  placed  in  the  work.  The  same  stone  will  vary 
greatly  in  its  durability  according  to  the  nature  and  extent  of  the 
atmospheric  influences  to  which  it  is  subjected. 

The  sulphur  acids,  carbonic  acid,  hydrochloric  acid,  and  traces 
of  nitric  acid,  in  the  smoky  air  of  cities  and  towns,  and  the  carbonic- 
acid  in  the  atmosphere  ultimately  decompose  any  stone  of  which 
either  carbonate  of  lime  or  carbonate  of  magnesia  forms  a  consid- 
erable part. 

Wind  has  a  considerable  effect  upon  the  durability  of  stone. 
High  winds  blow  sharp  particles  against  the  face  of  the  stone  and 
thus  grind  it  away.  Moreover,  it  forces  the  rain  into  the  pores  of 


MASONRY  CONSTRUCTION 


the  stone,  and  may  thus  cause  a  considerable*  depth  to  be  subject 
to  the  effects  of  acids  and  frost. 

In  winter  water  penetrates  porous  stones,  freezes,  expands,  and 
disintegrates  the  surface,  leaving  a  fresh  surface  to  be  similarly 
acted  upon. 

Strength  is  generally  an  indispensable  attribute,  especially 
under  compression  and  cross-strain. 

Cheapness  is  influenced  by  the  ease  with,  which  the  stone  can 
be  quarried  and  worked  into  the  various  forms  required.  Cheapness 
is  also  affected  by  abundance,  facility  of  transportation,  and  prox- 
imity to  the  place  of  use. 

Appearance.  The  requirement  of  beauty  is  that  it  should 
have  a  pleasing  appearance.  For  this  purpose  all  varieties  contain- 
ing much  iron  should  be  rejected,  as  they  are  liable  to  disfigurement 
from  rust-stains  caused  by  the  oxidation  of  the  iron  under  the  influ- 
ence of  the  atmosphere. 

TESTS    FOR  STONE. 

The  relative  enduring  qualities  of  different  stones  are  usually 
ascertained  by  noting  the  weight  of  water  they  absorb  in  a  given 
time.  The  best  stones  as  a  rule  absorb  the  smallest  amount  of  water. 

Some  stones,  however,  come  from  the  quarry  soaked  with  water 
and  in  that  condition  are  very  soft  and  easily  worked.  Upon  expo- 
sure to  the  atmosphere  they  gradually  dry  out  and  become  very  hard 
and  durable.  The  Bedford  limestone  of  Indiana  forms  an  example 
of  this  kind  of  stone,  and  the  stone  in  many  of  the  public  buildings 
throughout  the  United  States  may  be  seen  in  the  process  of  "weath- 
ering", indicated  by  the  mottled  appearance  of  the  walls. 

To  determine  the  absorptive  power,  dry  a  specimen  and  weigh 
it  carefully,  then  immerse  it  in  water  for  24  hours  and  weigh  again. 
The  increase  in  weight  will  be  the  amount  of  absorption. 

TABLE  1. 
Absorptive  Power  of  Stones. 

Percentage  of  Water 
Absorbed. 

Granites 0.00  to  0. 15 

Sandstones 0.41    "   5.48 

Limestones 0.20   "  5.00 

Marbles  ,  .  0.08   "  0.16 


MASONRY  CONSTRUCTION 


Effect  of  Frost  (Brard's  Test).  To  ascertain  the  effect  of 
frost,  small  pieces  of  the  stone  are  immersed  in  a  concentrated  boiling 
solution  of  sulphate  of  soda  (Glauber's  salts),  and  then  hung  up  for 
a  few  days  in  the  air.  The  salt  crystallizes  in  the  pores  of  the  stone, 
sometimes  forcing  off  bits  from  the  corners  and  arrises,  and  occa- 
sionally detaching  larger  fragments. 

The  stone  is  weighed  before  and  after  submitting  it  to  the  test. 
The  difference  of  weight  gives  the  amount  detached  by  disintegra- 
tion. The  greater  this  is,  the  worse  is  the  quality  of  the  stone. 

Effect  of  the  Atmosphere  (Acid  Test).  Soaking  a  stone 
for  several  days  in  water  containing  i  per  cent  of  sulphuric  and 
hydrocholric  acids  will  afford  an  idea  as  to  whether  it  will  stand 
the  atmosphere  of  a  large  city.  If  the  stone  contains  any  matter 
likely  to  be  dissolved  by  the  gases  of  the  atmosphere,  the  water 
will  be  more  or  less  cloudy  or  muddy. 

A  drop  or  two  of  acid  on  the  surface  of  a  stone  will  create  an  in- 
tense effervescence  if  there  is  a  large  proportion  present  of  carbon- 
ate of  lime  or  magnesia. 

PRESERVATION   OF   STONE. 

A  great  many  preparations  have  been  used  for  the  prevention 
of  the  decay  of  building  stones,  as  paint,  coal-tar,  oil,  beeswax, 
rosin,  paraffine,  soft-soap,  soda,  etc.  All  of  the  methods  are  expen- 
sive, and  there  is  no  evidence  to  show  that  they  afford  permanent 
protection  to  the  stone- 

ARTIFICIAL  STONES. 

Brick  is  an  artificial  stone  made  by  submitting  clay,  which  lias 
been  suitably  prepared  and  moulded  into  shape,  to  a  teftiperature 
of  sufficient  intensity  to  convert  it  into  a  semi-vitrified  state.  The 
quality  of  the  brick  depends  upon  the  kind  of  clay  used  and  upon 
the  care  bestowed  on  its  preparation. 

The  clays  of  which  brick  is  made  are  chemical  compounds  con- 
sisting of  silicates  of  alumina,  either  alone  or  combined  with  other 
substances,  such  as  iron,  lime,  soda,  potash,  magnesia,  etc.,  all  of 
which  influence  the  character  and  quality  of  the  brick,  according  as 
one  or  the  other  of  those  substances  predominates. 


MASONRY  CONSTRUCTION 


TABLE  2. 
Specific  Gravity,  Weight  and  Resistance  to  Crushing  of  Stones. 


Kinds  of  Stone 

Specific  Gravity 

Weight,  pounds 
per  cubic  foot 

Resistance  to 
crushing,  pounds 
per  sq.  in. 

Granite  — 
minimum  .    .    

2.60 

163 

12,000 

maximum..  .        

2.80 

176 

35,000 

Trap- 

minimum  . 

2  86 

178 

19000 

maximum  
Gneiss  average 

3.03 
2  70 

189 

168 

24,000 
19600 

Syenite,  average  . 

2.64 

167 

30,740 

Sandstones  — 
minimum  . 

2.23 

137 

5,000 

maximum.. 

2  75 

170 

18,000 

Limestones  — 
minimum 

1  90 

118 

7000 

maximum 

2  75 

175 

20000 

Marbles  — 
minimum  ... 

2.62 

165 

8,000 

maximum.. 

2.95 

179 

20,000 

Iron  gives  hardness  and  strength;  hence  the  red  brick  of  the 
Eastern  States  is  often  of  better  quality  than  the  white  and  yellow 
brick  made  in  the  West,  Silicate  of  lime  renders  the  clay  too  fusible 
and  causes  the  bricks  to  soften  and  to  become  distorted  in  the  pro- 
cess of  burning.  Carbonate  of  lime  is  at  high  temperatures  changed 
into  caustic  lime,  renders  the  clay  fusible,  and  when  exposed  to  the 
action  of  the  weather  absorbs  moisture,  promotes  disintegration,  and 
prevents  the  adherence  of  the  mortar.  Magnesia  exerts  but  little 
influence  on  the  quality;  in  small  quantities  it  renders  the  clay  fusible; 
at  60°  F.  its  crystals  lose  their  water  of  crystallization,  and  cold  water 
decomposes  them,  forming  an  insoluble  hydrate  in  the  form  of  a  white 
powder.  In  air-dried  brick  this  action  causes  cracking.  The  alkalies 
are  found  in  small  quantities  in  the  best  of  clays;  their  presence  tends 
to  promote  softening,  and  this  goes  on  the  more  rapidly  if  it  has 
been  burned  at  too  low  a  temperature.  Sand  mixed  with  the  clay 
.in  moderate  quantity  (one  part  of  sand  to  four  of  clay  is  about  the 
best  proportion)  is  beneficial,  as  tending  to  prevent  excessive  shrinking 
in  the  fire.  Excess  of  sand  destroys  the  cohesion  and  renders  the 
brick  brittle  and  weak. 


MASONRY  CONSTRUCTION 


MANUFACTURE   OF    BRICK. 

The  manufacture  of  brick  may  be  classified  under  the  following 
heads : 

Excavation  of  Ihc  clay,  either  by  manual  or  mechanical  power. 

Preparation  of  ihe  clay  consists  in  (a)  removing  stones  and  me- 
chanical impurities;  (b)  tempering  and  moulding,  which  is  now 
done  almost  wholly  by  machinery.  There  is  a  great  variety  of 
machines  for  tempering  and  moulding  the  clay,  which,  however, 
may  be  grouped  into  three  classes,  according  to  the  condition  of 
the  clay  when  moulded:  (1)  soft-mud  machines,  for  which  the  clay 
is  reduced  to  a  soft  mud  by  adding  about  one  quarter  of  its  volume 
of  water;  (2)  stiff-mud  machines,  for  which  the  clay  is  reduced  to 
a  stiff  mud;  (3)  dry-clay  machines,  with  which  the  dry  or  nearly  dry 
clay  is  forced  into  the  moulds  by  a  heavy  pressure  without  having 
been  reduced  to  a  plastic  mass.  These  machines  may  also  be  divided 
into  two  classes,  according  to  the  method  of  filling  the  moulds:  (1) 
those  in  wrhich  a  continuous  stream  of  clay  is  forced  from  the  pug- 
mill  through  a  die  and  is  afterwards  cut  up  into  bricks;  and  (2)  those 
in  which  the  clay  is  forced  into  moulds  moving  under  the  nozxle  of 
the  pug-mill. 

Drying  and  Burning.  The  bricks,  having  been  dried  in  the 
open  air  or  in  a  drying-house,  are  burned  in  kilns;  the  time  of  burn- 
ing varies  with  the  character  of  the  clay,  the  form  and  si/e  of  the  kiln, 
and  the  kind  of  fuel,  from  six  to  fifteen  days. 

Color  of  Bricks  depends  upon  the  composition  of  the  clay, 
the  moulding  sand,  temperature  of  burning,  and  volume  of  air  ad- 
mitted to  the  kiln.  Pure  clay  free  of  iron  wrill  burn  white,  and 
mixing  of  chalk  writh  the  clay  will  produce  a  like  effect.  Iron  pro- 
duces a  tint  ranging  from  red  and  orange  to  light  yellow,  according  to 
the  proportion  of  the  iron. 

A  large  proportion  of  oxide  of  iron  mixed  with  pure  clay  will 
produce  a  bright  red,  and  where  there  is  from  S  to  10  per  cent,  and 
the  brick  is  exposed  to  an  intense  heat,  the  oxide  fuses  and  produces  a 
dark  blue  or  purple,  and  with  a  small  volume  of  manganese  and  an 
increased  proportion  of  the  oxide  the  color  is  darkened  even  to  a  black. 

A  small  volume  of  lime  and  iron  produces  a  cream  color,  an  in- 
crease of  iron  produces  red,  and  an  increase  of  lime  brutrn  Magnesia 


MASONRY  CONSTRUCTION 


in  presence  of  iron  produces  yellow,  and  clay  containing  alkalies  and 
burned  at  a  high  temperature  produces  a  bluish  green. 

The  best  quality  of  building  brick  arid  probably  the  majority 
of  paving  brick  or  block,  are  manufactured  from  shale.  The  process 
of  manufacture  is  similar  to  that  of  clay-brick,  the  shale  being  first 
ground  very  fine.  If  the  shale  is  nearly  free  from  impurities,  the 
resulting  product  will  be  a  cream  colored  brick.  To  give  the  brick 
any  desired  color,  the  shale  is  mixed  with  clay  containing  the  proper 
proportions  of  lime,  iron,  or  magnesia,  giving  almost  any  shade  from 
a  cream  to  a  dark  wine  color  or  even  a  black. 

Classification  of  Brick.  Bricks  are  classified  according  to  (1) 
the  way  in  which  they  are  moulded;  (2)  their  position  in  the  kiln 
while  being  burned;  and  (3)  their  form  or  use. 

The  method  of  moulding  gives  rise  to  the  following  terms: 

Soft-mud  Brick.  One  moulded  from  clay  which  has  been  re- 
duced to  a  soft  mud  by  adding  water.  It  may  be  either  hand-moulded 
or  machine-moulded. 

Stiff-mud  Brick.  One  moulded  from  clay  in  the  condition  of 
stiff  mud.  It  is  always  machine-moulded. 

Pressed  Brick.     One  moulded  from  dry  or  semi-dry  clay. 

Re-pressed  Brick.  A  soft-mud  brick  which,  after  being  par- 
tially dried,  has  been  subjected  to  an  enormous  pressure.  It  is  also 
called,  but  less  appropriately,  pressed  brick.  The  object  of  the 
re-pressing  is  to  render  the  form  more  regular  and  to  increase  the 
strength  and  density. 

Sanded  Brick.  Ordinarily,  in  making  soft-mud  brick,  sand 
is  sprinkled  into  the  moulds  to  prevent  the  clay  from  sticking;  the 
brick  is  then  called  sanded  brick.  The  sand  on  the  surface  is  of 
no  advantage  or  disadvantage.  In  hand-moulding,  when  sand  is 
used  for  this  purpose,  it  is  certain  to  become  mixed  with  the  clay 
and  occur  in  streaks  in  the  finished  brick,  which  is  very  undesirable. 

Machine-made  Brick.  Brick  is  frequently  described  as  " machine 
made";  but  this  is  very  indefinite,  since  all  grades  and  kinds  are 
made  by  machinery. 

When  brick  was  generally  burned  in  the  old-style  up-draught 
kiln,  the  classification  according  to  position  was  important;  but  with 
the  new  styles  of  kilns  and  improved  methods  of  burning,  the  quality 
is  so  nearly  uniform  throughout  the  kiln  that  the  classification  is  less 


MASONRY  CONSTRUCTION 


important.     Three  grades  of  brick  are  taken  from  the  old-style  kiln: 

Arch  or  Clinker  Bricks.  Those  which  form  the  tops  and  sides 
of  the  arches  in  which  the  fire  is  built.  Being  overburned  and  par- 
tially vitrified,  they  are  hard,  brittle,  and  weak. 

Body,  Cherry,  or  Hard  Bricks.  Those  taken  from  the  interior 
of  the  pile.  The  best  bricks  in  the  kiln. 

Salmon,  Pale,  or  Soft  Bricks. .  Those  which  form  the  exterior 
of  the  mass.  Being  imderburned,  they  are  too  soft  for  ordinary 
work,  unless  it  be  for  filling.  The  terms  salmon  and  pale  refer  to  the 
color  of  the  brick,  and  hence  are  not  applicable  to  a  brick  made  of  a 
clay  that  does  not  burn  red.  Although  nearly  all  brick-clays  burn 
red,  yet  the  localities  where  the  contrary  is  true  are  sufficiently  numer- 
ous to  make  it  desirable  to  use  a  different  term  in  designating  the 
quality.  There  is  not  necessarily  any  relation  between  color,  and 
strength  and  density.  Brick-makers  naturally  have  a  prejudice 
against  the  term  soft  brick,  which  doubtless  explains  the  nearly  uni- 
versal prevalence  of  the  less  appropriate  term  salmon. 

The  form  or  use  of  bricks  gives  rise  to  the  following  classification : 

Compass  Brick.  Those  having  one  edge  shorter  than  the  other. 
Used  in  lining  shafts,  etc. 

Feather-edge  Brick.  Those  of  which  one  edge  is  thinner  than 
the  other.  Used  in  arches;  and  more  properly,  but  less  frequently, 
called  voussoir  brick. 

Front  or  Face  Brick.  Those  which,  owing  to  uniformity  of  size 
and  color,  are  suitable  for  the  face  of  the  walls  of  buildings.  Some- 
times face  bricks  are  simply  the  best  ordinary  brick;  but  generally 
the  term  is  applied  only  to  re-pressed  or  pressed  brick  made  especially 
for  this  purpose.  They  are  a  little  larger  than  ordinary  bricks. 

Sewer  Brick.     Ordinary  hard  brick,  smooth,  and  regular  in  form. 

Kiln-run  Brick.  All  the  brick  that  are  set  in  the  kiln  when 
burned. 

Hard  Kiln-run  Brick.  Brick  burned  hard  enough  for  the  face 
of  outside  walls,  but  taken  from  the  kiln  unselected. 

Rank  of  Bricks.  In  regularity  of  form  re-pressed  brick  ranks 
first,  dry-kiln  brick  next,  then  stiff-mud  brick,  and  soft-mud  brick 
last.  Regularity  of  form  depends  largely  upon  the  method  of  burning. 

The  compactness  and  uniformity  of  texture,  which  greatly  in- 
fluence the  durability  of  brick,  depend  mainly  upon  the  method  of 


MASONRY  CONSTRUCTION 


moulding.  As  a  general  rule,  hand-moulded  bricks  are  best  in  this 
respect,  sine®  the  clay  in  them  is  more  uniformly  tempered  before 
being  moulded;  but  this  advantage  is  partially  neutralized  by  the 
presence  of  sand-seams.  Machine-moulded  soft-mud  bricks  rank 
next  in  compactness  and  uniformity  of  texture.  Then  come  machine- 
moulded  stiff-mud  bricks,  which  vary  greatly  in  durability  with  the 
kind  of  machine  used  in  their  manufacture.  By  some  of  the  machines 
the  brick  is  moulded  in  layers  (parallel  to  any  face,  according  to  the 
kind  of  machine)  which  are  not  thoroughly  cemented,  and  which 
separate  under  the  action  of  frost.  The  dry-clay  brick  comes  last. 
However,  the  relative  value  of  the  products  made  by  different  pro- 
cesses varies  with  the  nature  of  the  clay  used. 

TABLE  3. 
Size  and  Weight  of  Bricks. 

The  variations  in  the  dimensions  of  brick  render  a  table  of  exact 
dimensions  impracticable. 

As  an  exponent,  however,  of  the  ranges  of  their  dimensions, 
the  following  averages  are  given: 

Baltimore  front "j 

Wilmington  front f-  8\ r  in.  X  4J  in.  X  2|  in. 

Washington  front j 

Croton  front 8J  in.  X  4    in.  X  2}  in. 

Maine  ordinary 7J  in'.  X  3| ;  in.  X  2|  in. 

Milwaukee  ordinary 8-J-  in.  X  4J  in.  X  2|  in. 

•North  River,  N.  Y 8    in.  X  3 J-  in.  X  2}  in. 

English , 9    in.  X  4J  in.  X  2J  in. 

The  Standard  Size  as  adopted  by  the  National  Brickmakers'  Asso- 
ciation and  the  National  Traders  and  Builders'  Association  is  for  com- 
mon brick  8}  X  4  X  2f  inches,  and  for  face  brick  8|  X  4  J  X  2£  inches. 
Re-pressed  Brick  weighs  about  150  Ib.  per  cubic  foot,  common  brick 
125,  inferior  soft  100.     Common  bricks  will  average  about  4J  Ib.  each. 
Hollow  Brick,  used  for  interior  walls  and  furring,  are  usually 
of  the  following  dimensions: 

Single,     8  in.  long,  3|  in.  wide,  2j  in.  thick. 
Double,  8  "      "     7i  "      "     4J  " 
Treble,    8  "       "     7*  " .     "     7}  "        " 
Roman  Brick,  12  in.  long,  4  to  4J  in.  wide,  1J  in.  thick. 


10 


MASONRY  CONSTRUCTION 


TABLE  4. 
Specific  Gravity,  Weight,  and  Resistance  to  Crushing  of  Brick, 


Designation  of  brick. 

Specific  gravity. 

Weight  per  cubic- 
foot,  pounds. 

Resistance  to 
Crushing,  pounds 
per  sq.  in. 

Best  pressed. 

2.4 

150 

5,000  to  14  973 

Common  hard;  
Soft  . 

1.0  to  2.0 
1  4 

125 

100 

."•),()()()  to    <S,000 
!.")()  to        (JOG 

Fire-Brick  are  used  wherever  high  temperatures  are  to  he 
resisted.  They  are  made  from  fire-clay  by  processes  very  similar 
to  those  adopted  in  making  ordinary  brick.  Fire-clay  is  also  used 
in  the  manufacture  of  paving-blocks  or  pavers,  especially  in  West- 
ern Indiana;  and  many  of  the  streets  of  our  Western  cities  are  laid 
with  fire-clay  block,  forming  a  smooth  and  durable  roadway. 

Fire-clay  may  be  defined  as  native  combinations  of  hyd  rated 
silicates  of  alumina,  mechanically  associated  with  silica  and  alumira 
in  various  states  of  subdivision,  and  sufficiently  free  from  silicates  of 
the  alkalies  and  from  iron  and  lime  to  resist  vitrification  at  high  tem- 
peratures. The  presence  of  oxide  of  iron  is  very  injurious;  and,  as 
a  rule,  the  presence  of  G  per  cent  justifies  the  rejection  of  the  brick. 
The  presence  of  3  per  cent  of  combined  lime,  soda,  potash,  and  mag- 
nesia should  be  a  cause  for  rejection.  The  sulphide  of  iron— pyrites 
—is  even  worse  than  the  substances  first  named. 

A  good  fire-clay  should  contain  from  52  to  80  per  cent  of  silica 
and  1 8  to  35  per  cent  of  alumina  and  have  a  uniform  texture,  a  some- 
what greasy  feel,  and  be  free  from  any  of  the  alkaline  earths. 

Good  fire  brick  should  be  uniform  in  size,  regular  in  shape, 
homogeneous  in  texture  and  composition,  strong,  and  infusible  and 
break  with  a  uniform  and  regular  fracture. 

A  properly  burnt  fire-brick  is  of  a  uniform  color  throughout  its 
mass.  A  dark  central  patch  and  concentric  rings  of  various  shades 
of  color  are  due  mainly  to  the  different  states  of  oxidation  of  the 
iron  and  partly  to  the  presence  of  unconsumed  carbonaceous  mat- 
ter, and  indicates  that  the  brick  was  burned  too  rapidly. 

Fire-brick  are  made  in  various  forms  to  suit  the  required  work. 
A  straight  brick  measures  9  X  4J  X  2-J  inches  and  weighs  about  7  Ib. 


MASONRY  CONSTRUCTION  11 

or  120  Ib.  per  cubic  foot;  specific  gravity  1.93.  One  cubic  foot  of 
wall  requires  17  9-inch  bricks;  one  cubic  yard  requires  460.  One 
ton  of  fire-clay  should  be  sufficient  to  lay  3000  ordinary  bricks. 
English'  fire-bricks  measure  9  X  44  X  2J  inches. 

To  secure  the  best  results  fire-brick  should  be  laid  in  the  same 
clay  from  which  they  are  manufactured.  It  should  be  used  as  a 
thin  paste,  and  not  as  mortar:  the  thinner  the  joint  the  better  the 
furnace  wall.  The  brick  should  be  dipped  in  water  as  they  are 
used,  so  that  when  laid  they  will  not  absorb  the  water  from  the 
clay  paste.  They  should  then  receive  a  thin  coating  of  the  prepared 
fire-clay,  and  be  carefully  placed  in  position  with  as  little  of  the  fire- 
clay as  possible. 

CEnENTINQ   flATERIALS. 

Composition.  All  the  cementing  materials  employed  in  build- 
ings are  produced  by  the  burning  of  natural  or  artificial  mixtures 
of  limestone  with  clay  or  siliceous  material.  The  active  substances 
in  this  process  and  the  ones  which  are  necessary  for  the  production 
of  a  cement,  are  the  burned  lime,  the  silica  and  the  alumina,  all  of 
which  enter  into  chemical  combination  with  one  another  under  the 
influence  of  a  high  temperature. 

Classification.  Owing  to  the  varying  composition  of  the  raw 
materials,  which  range  from  pure  carbonate  of  lime  to  stones  contain- 
ing variable  proportions  of  silica,  alumina,  magnesia,  oxide  of  iron, 
manganese,  etc.,  and  the  different  methods  employed  for  burning, 
the  product  possesses  various  properties  which  regulate  its  behavior 
when  treated  with  water,  and  render  necessary  certain  precautions 
in  its  manipulation  and  use,  and  furnishes  a  basis  for  division  into 
three  classes;  namely,  common  lime,  hydraulic  lime,  and  hydraulic 
cements,  the  individual  peculiarities  of  which  will  be  taken  up  later. 

Common  lime  is  distinguished  from  hydraulic  lime  by  its  failure 
to  set  or  harden  under  water,  a  property  which  is  possessed  by  hy- 
draulic lime  to  a  greater  or  less  degree. 

The  limes  are  distinguished  from  the  cements  by  the  former 
falling  to  pieces  (slaking)  on  the  application  of  water,  while  the 
latter  must  be  mechanically  pulverized  before  they  can  be  used. 

The  hydraulic  cements  are  divided  into  two  classes,  namely, 
natural  and  artificial.  The  first  class  includes  all  hydraulic  substances 


12  MASONRY  CONSTRUCTION 


produced  from  natural  mixtures  of  lime  and  clay,  by  a  burning  pro- 
cess which  has  not  been  carried  to  the  point  of  vitrification,  and  which 
still  contain  more  or  less  free  lime. 

The  artificial  cements  are  generally  designated  by  the  name 
"Portland"  and  comprise  all  the  cements  produced  from  natural  or 
artificial  mixtures  of  lime  and  clay,  lime  and  furnace  slag,  etc.,  by  a 
burning  process  which  is  carried  to  the  point  of  vitrification. 

The  hydraulic  cements  do  not  slake  after  calcination,  differing 
materially  in  this  particular  from  the  limes  proper.  They  can  be 
formed  into  paste  with  water,  without  any  sensible  increase  in  volume, 
and  little,  if  any,  production  of  heat,  except  in  certain  instances  among 
those  varieties  which  contain  the  maximum  amount  of  lime.  They 
do  not  shrink  in  hardening,  like  the  mortar  of  rich  lime,  and  can  be 
used  with  or  without  the  addition  of  sand,  although  for  the  sake  of 
economy  sand  is  combined  with  them. 

All  the  limes  and  cements  in  practical  use  have  one  feature  in 
common,  namely,  the  property  of  "setting"  or  "hardening"  when 
combined  with  a  certain  amount  of  water.  The  setting  of  a  cement 
is,  in  general,  a  complex  process,  partly  chemical  in  its  nature  and 
partly  mechanical.  Broadly  stated,  the  chemical  changes  wrhich 
occur  may  be  said  to  afford  opportunity  for  the  mechanical  changes 
which  result  in  hardening,  rather  than  themselves  to  cause  the  harden- 
ing. The  chemical  changes  are,  therefore,  susceptible  of  wide  varia- 
tion without  materially  influencing  the  result.  The  crumbling  which 
calcined  lime  undergoes  on  being  slaked  is  simply  a  result  of  the 
mechanical  disintegrating  action  of  the  evolved  steam.  In  some 
cements  of  which  plaster  of  Paris  may  be  taken  as  the  type,  water 
simply  combines  with  some  constituent  of  the  cement  already  present. 
In  others,  of  which  Portland  cement  is  the  most  important  example, 
certain  chemical  reactions  must  first  take  place.  These  reactions 
give  rise  to  substances  which,  as  soon  as  formed,  combine  with  water 
and  constitute  the  true  cementitious  material.  The  quantity  of 
water  used  should  be  regulated  according  to  the  kind  of  cement,  since 
every  cement  has  a  certain  capacity  for  water.  However,  in  practice 
an  excess  of  about  50  per  cent  must  be  used  to  aid  manipulation. 

The  rapidity  of  setting  (denominated  activity)  varies  with  the 
character  of  the  cement,  and  is  influenced  to  a  great  extent  by  the 
temperature,  and  also,  but  in  less  degree,  by  the  purity  of  the  water. 


:'  HE 

UNIVERSITY 

OF 


MASONRY  CONSTRUCTION  13 


Sea  water  hinders  the  setting  of  some  cements,  and  some  cements, 
which  are  very  hard  in  fresh  water,  only  harden  slightly  in  sea  water 
or  even  remain  soft.  Cements  which  require  more  than  one-half 
hour  to  set  are  called  "slow-setting",  all  others  "quick-setting". 
As  a  rule  the  natural  cements  are  quick-  and  the  Portlands  slow- 
setting.  None  of  the  cements  attain  their  maximum  hardness  until 
some  time  has  elapsed.  For  good  Portland  15  days  usually  suffices 
for  complete  setting,  but  the  hardening  process  may  continue  for  a 
year  or  more. 

The  form  and  fineness  of  the  cement  particles  are  of  great  impor- 
tance in  the  setting  of  the  cement,  and  affect  the  cementing  and 
economic  value.  Coarse  particles  have  no  setting  power  and  act  as 
an  adulterant.  In  consequence  of  imperfect  pulverization  some 
cements  only  develop  three-fourths  of  their  available  activity,  one- 
fourth  of  the  cement  consisting  of  grains  so  coarse  as  to  act  merely 
like  so  much  sand.  The  best  cement  when  separated  from  its  fine 
particles  will  not  harden  for  months  after  contact  with  water,  but  sets 
at  once  if  previously  finely  ground. 

In  a  mortar  or  concrete  composed  of  a  certain  quantity  of  inert 
material  bound  together  by  a  cementing  material  it  is  evident  that  to 
obtain  a  strong  mortar  or  concrete  it  is  essential  that  each  piece  of 
aggregate  shall  be  entirely  surrounded  by  the  cementing  material, 
so  that  no  two  pieces  are  in  actual  contact.  Obviously,  then,  the 
finer  a  cement  the  greater  surface  will  a  given  weight  cover,  and  the 
more  economy  will  there  be  in  its  use.  The  proper  degree  of  fineness 
is  reached  when  it  becomes  cheaper  to  use  more  cement  in  propor- 
tion to  the  aggregate  than  to  pay  the  extra  cost  of  additional  grinding. 

Use.  Common  lime  is  used  almost  exclusively  in  making 
mortar  for  architectural  masonry.  Natural  cement  is  used  for 
masonry  where  great  ultimate  strength  is  not  as  important  as  initial 
strength  and  in  masonry  protected  from  the  weather.  Portland 
cement  is  used  for  foundations  and  for  all  important  engineering 
structures  requiring  great  strength  or  which  are  subject  to  shock; 
also  for  all  sub-aqueous  construction. 

LINES. 

Rich  Limes.  The  common  fat  or  rich  limes  are  those  obtained 
by  calcining  pure  or  very  nearly  pure  carbonate  of  lime.  In  slaking 


14  MASONRY  CONSTRUCTION 

they  augment  to  from  two  to  three  and  a  half  times  that  of  the  original 
mass.  They  will  not  harden  under  water,  or  even  in  damp  places 
excluded  from  contact  with  the  air.  In  the  air  they  harden  by  the 
gradual  formation  of  carbonate  of  lime,  due  to  the  absorption  of  car- 
bonic acid  gas. 

The  pastes  of  fat  lime  shrink  in  hardening  to  such  a  degree  that 
they  cannot  be  employed  for  mortar  without  a  large  dose  of  sand. 

Poor  Limes.  The  poor  or  meagre  limes  generally  contain 
silica,  alumina,  magnesia,  oxide  of  iron,  sometimes  oxide  of  man- 
ganese, and  in  some  cases  traces  of  the  alkalies,  in  relative  propor- 
tions which  vary  considerably  in  different  localities.  In  slaking  they 
proceed  sluggishly,  as  compared  with  the  rich  limes — the  action  only 
commences  after  an  interval  of  from  a  few  minutes  to  more  than  an 
hour  after  they  are  wetted;  less  water  is  required  for  the  process,  and 
it  is  attended  with  less  heat  and  increase  of  volume  than  in  the  case 
of  fat  limes. 

Hydraulic  Limes.  The  hydraulic  limes,  including  the  three 
subdivisions,  viz.,  slightly  hydraulic,  hydraulic,  and  eminently  hydra  n- 
lic,  are  those  containing  after  calcination  sufficient  of  such  foreign 
constituents  as  combine  chemically  with  lime  and  water  to  confer 
an  appreciable  power  of  setting  or  hardening  under  water  without 
the  access  of  air.  They  slake  still  slower  than  the  meagre  limes,  and 
with  but  a  small  augmentation  of  volume,  rarely  exceeding  30  per 
cent  of  the  original  bulk. 

Lime  is  shipped  either  in  bulk  or  in  barrels.  If  in  bulk,  it  is 
impossible  to  preserve  it  for  any  considerable  length  of  time.  A 
barrel  of  lime  usually  weighs  about  230  Ib.  net,  and  will  make  about 
three  tenths  of  a  cubic  yard  of  stiff  paste.  A  bushel  weighs  75  Ib. 

NATURAL  CEflENT. 

Rosendale  or  natural  cements  are  produced  by  burning  in  draw- 
kilns  at  a  heat  just  sufficient  in  intensity  and  duration  to  expel  the 
carbonic  acid  from  argillaceous  or  silicious  limestones  containing 
less  than  77  per  cent  of  carbonate  of  lime,  or  argillo-magnesian  lime- 
stone containing  less  than  77  per  cent  of  both  carbonates,  and  then 
grinding  the  calcined  product  to  a  fine  powder  between  millstones. 

Characteristics.  The  natural  cements  have  a  porous,  globu- 
lar texture.  They  do  not  heat  up  nor  swell  sensibly  when  mixed  with 


MASONRY  CONSTRUCTION  15 


water.  They  set  quickly  in  air,  but  harden  slowly  under  water, 
without  shrinking,  and  attain  great  strength  with '  well-developed 
adhesive  force. 

S eft ing .  A  pat  made  with  the  minimum  amount  of  water  should 
set  in  about  30  minutes. 

Fineness.     At  least  93  per  cent  must  pass  through  a  No.  50  sieve. 

Weight.     Varies  from  49  to  56  pounds  per  cubic  foot. 

Specific  Gravity  about  2.70. 

Tensile  Strength.  Neat  cement,  one  day,  from  40  to  80  pounds. 
Seven  days,  from  60  to  100  pounds.  One  year,  from  300  to  400 
pounds. 

PORTLAND   CEHENT. 

Portland  Cement  is  produced  by  burning,  with  a  heat  of  suf- 
ficient intensity  and  duration  to  induce  incipient  vitrification,  certain 
argillaceous  limestones,  or  calcareous  clays,  or  an  artificial  mixture  of 
carbonate  of  lime  and  clay,  and  then  reducing  the  burnt  material  to 
powder  by  grinding.  Fully  95  per  cent  of  the  Portland  cement  pro- 
duced is  artificial.  The  name  is  derived  from  the  resemblance  which 
hardened  mortar  made  of  it  bears  to  a  stone  found  in  the  isle  of  Port- 
land, off  the  south  coast  of  England. 

The  quality  of  Portland  cement  depends  upon  the  quality  of  the 
raw  materials,  their  proportion  in  the  mixture,  the  degree  to  which 
the  mixture  is  burnt,  the  fineness  to  which  it  is  ground,  and  the  con- 
stant and  scientific  supervision  of  all  the  details  of  manufacture. 

Characteristics.  The  color  should  be  a  dull  bluish  or  green- 
ish gray,  caused  by  the  dark  ferruginous  lime  and  the  intensely  green 
manganese  salts.  Any  variation  from  this  color  indicates  the  pres- 
ence of  some  impurity;  blue  indicates  an  excess  of  lime;  dark  green, 
a  large  percentage  of  iron;  brown,  an  excess  of  clay;  a  yellowish  shade 
indicates  an  underburned  material. 

Fineness.  It  should  have  a  clear,  almost  floury  feel  in  the  hand; 
a  gritty  feel  denotes  coarse  grinding. 

Specific  Gravity  is  between  3  and  3.05.  As  a  rule  the  strength 
of  Portland  cement  increases  with  its  specific  gravity. 

Tensile  Strength.  When  moulded  neat  into  a  briquette  and 
placed  in  water  for  seven  days  it  should  be  capable  of  resisting  a  ten- 
sile strain  of  from  300  to  500  pounds  per  square  inch. 


16  MASONRY  CONSTRUCTION 

Setting.  A  pat  made  with  the  minimum  amount  of  water  should 
set  in  not  less  than  three  hours,  nor  take  more  than  six  hours. 

Expansion  and  Contraction.  Pats  left  in  the  air  or  placed  in 
water  should  during  or  after  setting  show  neither  expansion  nor  con- 
traction, either  by  the  appearance  of  cracks  or  change  of  form. 

A  cement  that  possesses  the  foregoing  properties  may  be  con- 
sidered a  fair  sample  of  Portland  cement  and  would  be  suitable  for 
any  class  of  work. 

Overtimed  Cement  is  likely  to  gain  strength  very  rapidly  in  the 
beginning  and  later  to  lose  its  strength,  or  if  the  percentage  of  free 
lime  be  sufficient  it  will  ultimately  disintegrate. 

Blowing  or  Swelling  of  Portland  cement  is  caused  by  too  much 
lime  or  insufficient  burning.  It  also  takes  place  when  the  cement  is 
very  fresh  and  has  not  had  time  to  cool. 

Adulteration.  Portland  cement  is  adulterated  with  slag  cement 
and  slaked  lime.  This  adulteration  may  be  distinguished  by  the 
light  specific  gravity  of  the  cement,  and  by  the  color,  which  is  of  a 
mauve  tint  in  powder,  while  the  inside  of  a  water-pat  when  broken 
is  deep  indigo.  Gypsum  or  sulphate  of  lime  is  also  used  as  an 
adulterant. 

TESTING   CEHENTS. 

The  quality  or  constructive  value  of  a  cement  is  generally  ascer- 
tained by  submitting  a  sample  of  the  particular  cement  to  a  series  of 
tests.  The  properties  usually  examined  are  the  color,  weight,  activity, 
soundness,  fineness  and  tensile  strength.  Chemical  analysis  is  some- 
times made,  and  specific  gravity  test  s  substituted  for  that  of  weight. 
Tests  of  compression  and  adhesion  are  also  sometimes  added.  As 
these  tests  cannot  be  made  upon  the  site  of  the  work,  it  is  usual  to 
sample  each  lot  of  cement  as  it  is  delivered  and  send  the  samples  to  a 
testing  laboratory. 

Sampling  Cement.  The  cement  is  sampled  by  taking  a  small 
quantity  (1  to  2  Ib.)  from  the  center  of  the  package.  The  number 
of  packages  sampled  in  any  given  lot  of  cement  will  depend  upon 
the  character  of  the  work,  and  varies  from  every  package  to  1  in  ."> 
or  1  in  10.  When  the  cement  is  brought  in  barrels  the  salnple  is 
obtained  by  boring  with  an  auger  either  in  the  head  or  center  of  the 
barrel,  drawing  out  a  sample,  then  closing  the  hole  with  a  piece  of 


MASONRY  CONSTRUCTION  17 


tin  firmly  tacked  over  it.  For  drawing  out  the  sample  a  brass  tube 
sufficiently  long  to  reach  the  bottom  of  the  barrel  is  used.  This  is 
thrust  into  the  barrel,  turned  around,  pulled  out,  and  the  core  of 
cement  knocked  out  into  the  sample-can,  which  is  usually  a  tin  box 
with  a  tightly  fitting  cover. 

Each  sample  should  be  labelled,  stating  the  number  of  the  sam- 
ple, the  number  of  bags  or  barrels  it  represents,  the  brand  of  the 
cement,  the  purpose  for  which  it  is  to  be  used,  the  date  of  delivery, 
and  date  of  sampling. 

FORM  OF  LABEL. 


Sample  No  ............  . 

No.  of  Barrels  .......... 

Brand  ....................... 

To  be  used 

Delivered  ..............  .  .      Sampled. 


The  sample  should  be  sent  at  once  to  the  testing  office,  and  none 
of  the  cement  should  be  used  until  the  report  of  the  tests  is  received. 

After  the.  report  of  the  tests  is  received  the  rejected  packages 
should  be  conspicuously  marked  with  a  "C"  and  should  be  removed 
without  delay;  otherwise  they  are  liable  to  be  used. 

Color.  The  color  of  a  cement  indicates  but  little,  since  it  is 
chiefly  due  to  oxides  of  iron  and  manganese,  which  in  no  way  affect 
the  cementitious  value;  but  for  any  given  kind  variations  in  shade 
may  indicate  differences  in  the  character  of  the  rock  or  in  the  degree 
of  burning.  The  natural  cements  may  have  almost  any  color  from 
the  very  light  straw  colored  "Utica"  through  the  brown  "Louisville", 
to  chocolate  "Rosendale".  The  artificial  Portlands  are  usually  a 
grayish  blue  or  green,  but  never  chocolate  colored. 

Weight.  For  any  particular  cement  the  weight  varies  with  the 
degree  of  heat  in  burning,  the  degree  of  fineness  in  grinding,  and  the 
density  of  packing.  The  finer  a  cement  is  ground  the  more  bulky 
it  becomes,  and  consequently  the  less  it  weighs.  Hence  light  weight 
may  be  caused  by  laudable  fine  grinding  or  by  objectionable  under- 
burning.  Other  things  being  the  same,  the  harder-burned  varieties 
are  the  heavier. 


18  MASONRY  CONSTRUCTION 


The  weight  per  unit  of  volume  is  usually  determined  by  sifting 
the  cement  into  a  measure  as  lightly  as  possible,  and  striking  the  top 
level  with  a  straight  edge.  In  careful  work  the  height  of  fall  should 
be  recorded.  Since  the  cement  absorbs  moisture,  the  sample  must 
be  taken  from  the  interior  of  the  package.  The  weight  per  cubic  foot 
is  neither  exactly  constant,  nor  can  it  be  determined  precisely.  The 
approximate  weight  of  cement  per  cubic  foot  is  as  follows: 

Portland,  English  and  German 77  to  90  Ib. 

fine-ground  French 09  " 

American... . 92  "  95  " 

Rosendale 49  "  50  " 

Roman 54  " 

A  bushel  contains  1.244  cubic  feet.  The  weight  of  a  bushel  can 
be  obtained  sufficiently  close  by  adding  25  per  cent  to  the  weight  per 
cubic  foot. 

Fineness.  The  cementing  and  economic  value  of  a  cement  is 
affected  by  the  degree  of  fineness  to  which  it  is  ground.  Coarse 
particles  in  a  cement  have  no  setting  power  and  act  as  an  adulterant. 

The  fineness  of  a  cement  is  determined  by  measuring  the  per- 
centage which  will  not  pass  through  sieves  of  a  certain  number  of 
meshes  per  square  inch.  Three  sieves  are  generally  used,  viz.: 

No.    50,    2,500  meshes  per  square  inch. 
No.    74,    5,476 
No.  100,  10,000 

Activity  denotes  the  speed  with  which  a  cement  begins  to  set. 
Cements  differ  widely  in  their  rate  and  manner  of  sdtiny.  Some 
occupy  but  a  few  minutes  in  the  operation,  and  others  require  several. 
Some  begin  setting  immediately  and  take  considerable  time  to  com- 
plete the  set,  while  others  stand  for  a  considerable  time  with  no  ap- 
parent action  and  then  set  very  quickly.  The  point  at  which  the  set 
is  supposed  to  begin  is  when  the  stiffening  of  the  mass  firxt  becomes 
perceptible,  and  the  end  of  the  set  is  when  cohesion  extends  through 
the  mass  sufficiently  to  offer  such  resistance  to  any  change  of  form 
as  to  cause  rupture  before  any  deformation  can  take  place. 

Test  of  Activity.  To  test  the  activity  mix  the  cement  with 
25  to  30  per  cent  of  its  weight  of  clean  water,  having  a  temperature 
of  between  05°  F.  and  70°  F.,  to  a  stiff  plastic  mortar,  and  make  one 


MASONRY  CONSTRUCTION 


19 


or  two  rakes  or  pats  2  or  3  inches  in  diameter  and  about  J  inch  in 
thickness.  As  soon  as  the  cakes  are  prepared,  immerse  in  water  at 
05°  F.,  and  note  the  time  required  for  them  to  set  hard  enough  to  bear 
respectively  a  -^-inch  wire  loaded  to  weigh  J  pound,  and  a  ^-inch 
vvire  loaded  to  weigh  1  pound.  When  the  cement  bears  the  light 
weight,  it  is  said  to  have  begun  to  set;  when  it  bears  the  heavy  weight, 
it  is  said  to  have  entirely  set.  The  apparatus  employed  for  this  test 
is  shown  in  Fig.  1,  and  is  called  "Vicat's  Needle  apparatus". 


Fig.  1.    Vicat's  Needle  Apparatus. 

Quick  and  Slow  Setting.  The  aluminous  natural  cements 
are  commonly  "  quick-setting/'  though  not  always  so,  as  those  con- 
taining a  considerable  percentage  of  sulphuric  acid  may  set  quite 
slowly.  The  magnesian  and  Portland  varieties  may  be  either  "  quick  "• 
or  "slow".  Specimens  of  either  variety  may  be  had  that  will  set  at 
any  rate^  from  the  slowest  to  the  most  rapid,  and  no  distinction  can 
be  drawn  between  the  various  classes  in  this  regard. 

Water  containing  sulphate  of  lime  in  solution  retards  the  setting, 
This  fact  has  been  made  use  of  in  the  adulteration  of  cement,  pow- 
dered gypsum  being  mixed  with  it  to  make  it  slow-setting,  greatly  to 
the  injury  of  the  material. 


20  MASONRY  CONSTRUCTION 

The  temperature  of  the  water  used  affects  tne  time  required  for 
setting;  the  higher  the  temperature,  within  certain  limits,  the  more 
rapid  the  set.  Many  cements  which  require  several  hours  to  set  when 
mixed  with  water  at  a  temperature  of  40°  F.  will  set  in  a  few  minutes 
if  the  temperature  of  the  water  be  increased  to  80°  F.  Below  a  cer- 
tain inferior  limit,  ordinarily  from  30°  to  40°  F.,  the  cement  will  not 
set,  while  at  a  certain  upper  limit,  in  many  cements  between  100°  and 
140°  F.,  a  change  is  suddenly  made  from  a  very  rapid  to  a  very  slow 
rate,  which  then  continually  decreases  as  the  temperature  increases, 
until  practically  the  cement  will  not  set. 

The  quick-setting  cements  usually  set  so  that  experimental  sam- 
ples can  be  handled  within  5  to  30  minutes  after  mixing.  The  slow- 
setting  cements  require  from  1  to  8  hours.  Freshly  ground  cements 
set  quicker  than  older  ones. 

Soundness  denotes  the  property  of  not  expanding  or  contracting 
or  cracking  or  checking  in  setting.  These  effects  may  be  due  to  free 
lime,  free  magnesia,  or  to  unknown  causes.  Testing  soundness  is, 
therefore,  determining  whether  the  cement  contains  any  active  im- 
purity. An  inert  adulteration  or  impurity  affects  only  its  economic 
value;  but  an  active  impurity  affects  also  its  strength  and  durability. 

For  the  purpose  of  determining  the  amount  of  contraction  or 
expansion  the  "Bauschinger"  apparatus,  Fig.  2,  is  used.  A  mould 
is  used  in  which  the  test  bars  of  cement  are  formed. 

Tests  of  Soundness.  The  soundness  of  a  cement  may  be 
determined  by  cold  tests,  so-called,  the  cement  being  at  ordinary 
temperature;  or  by  accelerated  or  hot  tests. 

To  make  the  cold  tests,  prepare  small  cakes  or  pats  of  neat 
cement,  3  or  4  inches  in  diameter  and  about  one-half  inch  thick 
at  the  center,  tapering  to  a  thin  edge.  Place  the  samples  upon  a  piece, 
of  glass  and  cover  with  a  damp  cloth  for  a  period  of  24  hours  and  then 
immerse  glass  and  all  in  water  for  a  period  of  28  days  if  possibly, 
keeping  watch  from  day  to  day  to  see  if  the  samples  show  any  cracks 
or  signs  of  distortion. 

The  first  indication  of  inferior  quality  is  the  loosening  of  the  pat 
from  the  glass,  which  usually  takes  place  in  one  or  two  days.  Good 
cement  will  remain  firmly  attached  to  the  glass  for  two  weeks  at  least, 

The  ordinary  tests,  extending  over  a  proper  interval,  often  fail 
to  detect  unsoundness,  and  circumstances  may  render  the  ordinary 


MASONRY  CONSTRUCTION 


21 


tests  impossible  from  lack  of  time.  Under  such  circumstances  resort 
must  be  had  to  accelerated  tests,  which  may  be  made  in  several  ways. 
Warm=Water  Test.  Prepare  the  sample  as  before,  and  after 
allowing  it  to  set,  immerse  in  water  maintained  at  a  temperature  of 
from  100°  to  115°  F.  If  the  specimen  remains  firmly  attached  to  the 
glass  and  shows  no  cracks,  it  is  probably  sound. 


Fig.  2.    Bauschinger's  Apparatus. 

The  hot-water  test  is  similar  to  the  last,  but  the  water  is  main- 
tained at  a  temperature  of  from  195°  to  200°  F. 

The  boiling  test  consists  in  immersing  the  specimen  in  cold  water 
immediately  after  mixing  and  gradually  raising  the  temperature  of 
the  water  to  the  boiling  point,  continuing  the  boiling  for  three  hours. 

For  an  emergency  test,  the  specimen  may  be  prepared  as  before, 
and  after  setting  may  be  held  under  a  steam  cock  of  a  boiler  and  live 
steam  discharged  upon  it. 

The  results  of  accelerated  tests  must  not  be  accepted  too  literally, 
but  should  be  interpreted  in  the  light  of  judgment  and  experience. 


22  MASONRY  CONSTRUCTION 

The  cracking  or  contortion  of  the  specimen  (sometimes  called 
"blowing"),  is  due  to  the  hydration  and  consequent  expansion  of  the 
lime  or  magnesia.  If  the  effect  is  due  to  lime,  the  cement  can  be  im- 
proved by  exposure  to  the  air,  thus  allowing  the  free  lime  to  slake. 
This  treatment  is  called  "cooling  the  cement".  The  presence  of 
uncombined  magnesia  is  more  harmful  than  that  of  lime. 

Some  idea  of  the  quality  of  a  cement  may  be  gained  by  exposing 
to  the  air  a  small  cake  of  neat  cement  mortar  and  observing  its  color. 
"A  good  Portland  cement  should  be  uniform  bluish  gray  throughout, 
yellowish  blotches  indicate  poor  cement". 

Tests  of  soundness  should  not  only  be  carefully  conducted,  but 
should  extend  over  considerable  time.  Occasionally  cement  is  found 
which  seems  to  meet  the  usual  tests  for  soundness,  strength,  etc.,  and 
yet  after  considerable  time  loses  all  coherence  and  falls  to  pieces. 

Strength.  The  strength  is  usually  determined  by  submitting 
a  specimen  of  known  cross-section  (generally  one  square  inch)  to  a 
tensile  strain.  The  reason  for  adopting  a  tensile  test  is  that  since 
even  the  weakest  cement  cannot  be  crushed,  in  ordinary  practice, 
by  direct  compression,  and  since  cement  is  not  used  in  places  where 
cross  strain  is  brought  to  bear  upon  it,  torsion  being  out  of  the  ques- 
tion, the  only  valuable  results  can  be  derived  from  tests  for  tensile 
strength.  In  case  of  a  cracking  wall  the  strain  is  that  of  tension  due 
to  the  difference  of  the  direction  of  the  strain  caused  by  the  sinking 
of  one  part  of  the  wall. 

In  comparing  different  brands  of  cement  great  care  must  be 
exercised  to  see  that  the  same  kind  and  quality  of  sand  is  used  in 
each  case,  as  difference  in  the  sand  will  cause  difference  in  the  results. 
To  obviate  this  a  standard  sand  is  generally  used.  This  consists  of 
crushed  quartz  of  such  a  degree  of  fineness  that  it  will  all  pass  a  No. 
20  sieve  (400  meshes  to  the  square  inch;  wire  No.  28  Stubbs'  gauge) 
and  be  caught  on  a  No.  30  sieve  (900  meshes  to  the  square  inch;  wire 
No.  31  Stubbs'  gauge). 

Valuable  and  probably  as  reliable  comparative  tests  can  be  made 
with  the  sand  which  is  to  be  used  for  making  the  mortar  in  the  pro- 
posed work.  Specimens  of  neat  cement  are  also  used  for  testing, 
they  can  be  handled  sooner  and  will  show  less  variation  than  speci- 
mens composed  of  cement  and  sand. 


MASONRY  CONSTRUCTION 


23 


The  cement  is  prepared  for  testing  by  being  formed  into  a  stiff 
paste  by  the  addition  of  just  sufficient  water  for  this  purpose.  When 
sand  is  to  be  added,  the  exact  proportions  should  be  carefully  deter- 
mined by  weight  and  thoroughly  and  intimately  mixed  with  the  cement 
in  a  dry  state  before  the  water  is  added;  and,  so  far  as  possible,  all 
the  water  that  is  necessary  to  produce  the  desired  consistency  should 
be  added  at  once  and  thereafter  the  manipulation  with  the  spatula 
or  trowel  should  be  rapid  and  thorough.  The  mortar  so  obtained 
is  filled  into  a  mould  of  the  form  and  dimensions  shown  in  Fig.  3. 
These  moulds  are  usually  of  iron  or  brass.  Wooden  moulds,  if 
well  oiled  to  prevent  their  absorbing  water,  answer  the  purpose  well 
for  temporary  use,  but  speedily  become  unfit  for  accurate  work.  In 
filling  the  mould  care  must  be  exercised  to  complete  the  filling  before 
incipient  setting  begins. 

The  moulds  while  being 
charged  and  manipulated, 
should  be  laid  on  glass,  slate, 
or  some  other  non-absorbent 
material.  The  specimen,  now 
called  the  "briquette",  should 
be  removed  from  the  mould 
as  soon  as  it  is  hard  enough 
to  stand  it,  without  breaking.  Fig.  3.  Briquette  Mould. 

The  briquettes  are  then  im- 
mersed in  water,  where  they  should  remain  constantly  covered  until 
tested.  If  they  are  exposed  to  the  air,  the  water  may  be  carried 
away  by  evaporation  and  leave  the  mortar  a  pulverant  mass.  Also, 
since  the  mortar  does  not  ordinarily  set  as  rapidly  under  water  as 
in  the  air  (owing  to  the  difference  in  temperature),  it  is  necessary  for- 
accurate  work  to  note  the  time  of  immersion,  and  also  to  break  the 
briquette  as  soon  as  it  is  taken  from  the  water.  Cement  ordinarily 
attains  a  greater  strength  when  allowed  to  set  under  water,  but  attains 
it  more  slowly. 

Age  of  Briquette  for  Testing.  It  is  customary  to  break  part 
of  the  briquettes  at  the  end  of  seven  days,  and  the  remainder  at 
the  end  of  twenty-eight  days.  As  it  is  sometimes  impracticable  to 
wait  twenty-eight  days,  tests  are  often  made  at  the  end  of  one  and 
seven  days,  respectively.  The  ultimate  strength  of  the  cement  is 


MASONRY  CONSTRUCTION 


judged  by  the  increase  in  strength  between  the  two  dates.  A  mini- 
mum strength  for  the  two  dates  is  usually  specified. 

Testing  the  Briquettes.  When  taken  out  of  the  water  the 
briquettes  are  subjected  to  a  tensile  strain  until  rupture  takes  place  in 
a  suitably  devised  machine.  There  are  several  machines  on  the  mar- 
ket for  this  purpose.  Fig.  4  represents  one  which  is  extensively  used. 

To  make  a  test,  hang  the  cup  F  on  the  end  of  the  beam  Z),  as 
shown  in  the  illustration.  See  that  the  poise  R  is  at  the  zero  mark, 


Fig.  4.    Cement  Testing  Machine. 

and  balance  the  beam  by  turning  the  ball  L.  Fill  the  hopper  B  with 
fine  shot,  place  the  specimen  in  the  clamps  N  N,  and  adjust  the 
hand  wheel  P  so  that  the  graduated  beam  D  will  rise  nearly  to  the 
stop  K. 

Open  the  automatic  valve  J  so  as  to  allow  the  shot  to  run  slowly 
into  the  cup  F.  Stand  back  and  leave  the  machine  to  make  the  test. 

When  the  specimen  breaks,  the  graduated  beam  D  drops  and 
closes  the  valve  J,  remove  the  cup  with  the  shot  in  it,  and  hang  the 
counterpoise  weight  G  in  its  place. 


MASONRY  CONSTRUCTION 


25 


Hang  the  cup  F  on  the  hook  under  the  large  ball  E,  and  proceed 
to  weigh  the  shot  in  the  regular  way,  using  the  poise  R  on  the  gradu- 
ated beam  D,  and  the  weights  //  on  the  counterpoise  weight  G. 
The  result  will  show  the  number  of  pounds  required  to  break  the 
specimen. 

TABLE  5. 
Tensile  Strength  of  Cement  Mortar. 


Age  of  mortar  when  tested. 

Average  tensile  strength  in  pounds 
per  square  inch. 

Portland. 

Rosendale. 

CLEAR  CEMENT. 
One  hour,  or  until  set,  in  air,  the 
remainder  of  the  time  in  water: 
1  day  

Min. 
100 

250 
350 
450 

Max. 

140 

550 
700 

800 

Min. 

40 

60 
100 
300 

30 
50 
200 

Max. 

80 

100 
150 
400 

50 

-80 
300 

One  day  in  air,  the  remainder  of 
the  time  in  water: 
1  week  

4  weeks.. 

1  year  

1  PART  CEMENT  TO  1  PART  SAND. 
One  day  in  air,  the  remainder  of 
the  time  in  water: 
1  week  

4  weeks  

1  year  . 

1  PART  CEMENT  TO  3  PARTS  SAND. 
One  day  in  air,  the  remainder  of 
the  time  in  water: 
1  week  i  ....*... 

80 
100 
200 

125 
200 
350 

4  weeks  

1  year  . 

CEflENTS— flEflORANDA. 

Cement  is  shipped  in  barrels  or  in  cotton  or  paper  bags. 
The  usual  dimensions  of  a  barrel  are:   length  2  ft.  4  in.,  middle 
diameter  1  ft.  4^  in.,  end  diameter  1  ft.  3^  in. 
The  bags  hold  50,  100,  or  200  pounds. 


26  MASONRY  CONSTRUCTION 

A  barrel  weighs  about  as  follows  : 

Rosendale,  N.Y.  .................    ......  300  11).  net 

Rosendale,  Western  ............  ..........  205 

Portland  ..............................  375       " 

A  barrel  of  Rosendale  cemejit  contains  about  3.40  cubic  feet 
and  will  make  from  3.70  to  3.75  cubic  feet  of  stiff  paste,  or  79  to 
83  pounds  will  make  about  one  cubic  foot  'of  paste.  A  barrel  of 
Rosendale  cement  (300  Ib.)  and  two  barrels  of  sand  (7J  cubic^feet) 
mixed  with  about  half  a  barrel  of  water  will  make  about  8  cubic  feet 
of  mortar,  sufficient  for 

192  square  feet  of  mortar-joint  J  inch  thick. 


384      "  }     " 

768      "        "    "  "          £    " 

A  barrel  of  Portland  cement  contains  ibout  3.25  to  3.35  cubic 
feet  —  100  pounds  will  make  about  one  cubic  foot  of  stiff  paste. 

A  barrel  of  cement  measured  loosely  increases  considerably  in 
bulk.  The  following  results  were  obtained  by  measuring  in  quan- 
tities of  two  cubic  feet  : 

1  bbl.  Norton's  Rosendale  gave  ..........  4.37  cu.  ft. 

Anchor  Portland  gave  ............  3  .  65 

"       Sphinx  Portland  gave  ............  3.71       " 

"      Buckeye  Portland  gave..  .  .  ........  4.25       " 

Preservation  of  Cements.  Cements  require  to  be  stored  in 
a  dry  place  protected  from  the  weather;  the  packages  should 
not  be  placed  directly  on  the  ground,  but  on  boards  raised  a  few 
inches  from  it.  If  necessary  to  stack  it  out  of  doors  a  platform  of 
planks  should  first  be  made  and  the  pile  covered  with  canvas.  Port- 
land cement  exposed  to  the  atmosphere  will  absorb  moisture  until 
it  is  practically  ruined.  The  absorption  of  moisture  by  the  natural 
cements  will  cause  the  development  of  carbonate  of  lime,  which  will 
interfere  with  the  subsequent  hydration. 

niSCELLANEOUS   CEflENTS. 

Slag  Cements  are  those  formed  by  an  admixture  of  slaked  lime 
with  ground  blast-furnace  slag.  The  slag  used  has  approximately 
the  composition  of  an  hydraulic  cement,  being  composed  mainly  of 
silica  and  alumina,  and  lacking  a  proper  proportion  of  lime  to  render 


MASONRY  CONSTRUCTION  27 

it  active  as  a  cement.  In  preparing  the  cement  the  slag  upon  coming 
from  the  furnace  is  plunged  into  water  and  reduced  to  a  spongy  form 
from  which  it  may  be  readily  ground.  This  is  dried  and  ground  to  a 
fine  powder.  The  powdered  slag  and  slaked  lime  are  then  mixed 
in  proper  proportions  and  ground  together,  so  as  to  very  thoroughly 
distribute  them  through  the  mixture.  It  is  of  the  first  importance 
in  a  slag  cement  that  the  slag  be  very  finely  ground,  and  that  the 
ingredients  be  very  uniformly  and  intimately  incorporated. 

Both  the  composition  and  methods  of  manufacture  of  slag 
cements  vary  considerably  in  different  places.  They  usually  con- 
tain a  higher  percentage  of  alumina  than  Portland  cements,  and 
the  materials  are  in  a  different  state  of  combination,  as,  being  mixed 
after  the  burning,  the  silicates  and  aluminates  of  lime  formed  during 
the  burning  of  Portland  cement  cannot  exist  in  slag  cement. 

The  tests  for  slag  cement  are  that  briquettes  made  of  one  part 
of  cement  and  three  parts  of  sand  by  weight  shall  stand  a  tensile 
strain  of  140  pounds  per  square  inch  (one  day  in  air  and  six  in  water), 
and  must  show  continually  increasing  strength  after  seven  days,  one 
month,  etc.  At  least  90  per  cent  must  pass  a  sieve  containing  40,000 
meshes  to  the  square  inch,  and  must  stand  the  boiling  test. 

Pozzuolanas  are  cements  made  by  a  mixture  of  volcanic  ashes 
with  lime,  although  the  name  is  sometimes  applied  to  mixed  cements 
in  general.  The  use  of  pozzuolana  in  Europe  dates  back  to  the 
time  of  the  Romans. 

Roman  Cement  is  a  natural  cement  manufactured  from  the 
septaria  nodules  of  the  London  Clay  formation;  it  is  quick-setting, 
but  deteriorates  with  age  and  exposure  to  the  air. 

HORTAR. 

Ordinary  flortar  is  composed  of  lime  and  sand  mixed  into 
a  paste  with  water.  When  cement  is  substituted  for  the  lime,  the 
mixture  is  called  cement  mortar. 

Uses.  The  use  of  mortar  in  masonry  is  to  bind  together  the 
bricks  or  stones,  to 'afford  a  bed  which  prevents  their  inequalities 
from  bearing  upon  one  another  and  thus  to  cause  an  equal  distribu- 
tion of  pressure  over  the  bed.  It  also  fills  up  the  spaces  between 
the  bricks  or  stones  and  renders  the  wall  weathe"  tight.  It  is  also 
used  in  concrete  as  a  matrix  for  broken  stones  or  other  bodies  to  be 


28  MASONRY  CONSTRUCTION 


amalgamated  into  one  solid  mass;  and  for  plastering  and  other 
purposes. 

The  quality  of  mortar  depends  upon  the  character  of  the  materials 
used  in  its  manufacture,  their  treatment,  proportions,  and  method 
of  mixing.  • 

Proportions.  The  proportion  of  cement  to  sand  depends  upon 
the  nature  of  the  work  and  the  necessity  for  the  development  of 
strength  or  imperviousness.  The  relative  quantities  of  sand  and 
cement  should  also  depend  upon  the  nature  of  the  sand;  fine  sand 
requires  more  cement  than  coarse.  Usual  proportions  are: 

Lime  mortar,  1  part  of  lime  to  4  parts  of  sand. 

Natural  cement  mortar,  1  part  cement  to  2  or  3  parts  of  sand. 

Portland  cement  mortar,  1  part  cement  to  2,  3,  or  4  parts  of  sand, 
according  to  the  character  of  the  work. 

Sand  for  flortar.  The  sand  used  must  be  clean,  that  is,  free 
from  clay,  loam,  mud,  or  organic  matter;  sharp,  that  is,  the  grains 
must  be  angular  and  not  rounded  as  those  from  the  beds  of  rivers 
and  the  seashore;  coarse,  that  is,  it  must  be  large-grained,  but  not 
too  uniform  in  size. 

The  best  sand  is  that  in  which  the  grains  are  of  different  sizes; 
the  more  uneven  the  sizes  the  smaller  will  be  the  amount  of  voids, 
and  hence  the  less  cement  required. 

The  cleanness  of  sand  may  be  tested  by  rubbing  a  little  of  the 
dry  sand  in  the  palrn  of  the  hand,  and  after  throwing  it  out  noticing 
the  amount  of  dust  left  on  the  hand.  The  cleanness  may  also  be 
judged  by  pressing  the  sand  between  the  fingers  while  it  is  damp; 
if  the  sand  is  clean  it  will  not  stick  together,  but  will  immediately 
fall  apart  when  the  pressure  is  removed. 

The  sharpness  of  sand  can  be  determined  approximately  by 
rubbing  a  few  grains  in  the  hand  or  by  crushing  it  near  the  ear  and 
noting  if  a  grating  sound  is  produced;  but  an  examination  through 
a  small  lens  is  better. 

To  determine  the  presence  of  Salt  and  Clay.  Shake  up  a  small 
portion  of  the  sand  with  pure  distilled  water  in  a  perfectly  clean 
stoppered  bottle,  and  allow  the  sand  to  settle;  add  a  few  drops  of 
pure  nitric  acid  and  then  add  a  few  drops  of  solution  of  nitrate  of 
silver.  A  white  precipitate  indicates  a  tolerable  amount  of  salt;  a 
faint  cloudiness  may  be  disregarded. 


MASONRY  CONSTRUCTION  29 


The  presence  of  clay  may  be  ascertained  by  agitating  a  small 
quantity  of  the  sand  in  a  glass  of  clear  water  and  allowing  it  to  stand 
for  a  few  hours  to  settle;  the  sand  and  clay  will  separate  into  two 
well-defined  layers. 

Screening.  Sand  is  prepared  for  use  by  screening  to  remove 
the  pebbles  and  coarser  grains.  The  fineness  of  the  meshes  of  the 
screen  depends  upon  the  kind  of  work  in  which  the  sand  is  to  be  used. 

Washing.  Sand  containing  loam  or  earthy  matters  is  cleansed 
by  washing  with  water,  either  in  a  machine  specially  designed  for  the 
purpose  and  called  a  sand-washer,  or  by  agitating  with  water  in  tubs 
or  boxes  provided  with  holes  to  permit  the  dirty  water  to  flow  away. 

Water  for  flortar.  The  water  employed  for  mortar  should 
be  fresh  and  clean,  free  from  mud  and  vegetable  matter.  Salt  water 
may  be  used,  but  with  some  natural  cements  it  may  retard  the  setting, 
the  chloride  and  sulphate  of  magnesia  being  the  principal  retarding 
elements.  Less  sea-water  than  fresh  will  be  required  to  produce  a 
given  consistency. 

Quantity.  The  quantity  of  water  to  be  used  in  mixing  mortar 
can  be  determined  only  by  experiment  in  each  case.  It  depends 
upon  the  nature  of  the  cement,  upon  that  of  the  sand  and  of  the  water, 
and  upon  the  proportions  of  sand  to  cement,  and  upon  the  purpose 
for  which  the  mortar  is  to  be  used. 

Fine  sand  requires  more  water  than  coarse  to  give  the  same  con- 
sistency. Dry  sand  will  take  more  water  than  that  which  is  moist, 
and  sand  composed  of  porous  material  more  than  that  which  is  hard. 
As  the  proportion  of  sand  to  cement  is  increased  the  proportion  of 
water  to  cement  should  also  increase,  but  in  a  much  less  ratio. 

The  amount  of  water  to  be  used  is  such  that  the  mortar  when 
thoroughly  mixed  shall  have  a  plastic  consistency  suitable  for  the 
purpose  for  which  it  is  to  be  used. 

The  addition  of  water,  little  by  little,  or  from  a  hose,  should 
not  be  allowed. 

Cement  flortar.  In  mixing  cement  mortar  the  cement  and 
sand  are  first  thoroughly  mixed  dry,  the  water  then  added,  and  the 
whole  worked  to  a  uniformly  plastic  condition. 

The  quality  of  the  mortar  depends  largely  upon  the  thoroughness 
of  the  mixing,  the  great  object  of  which  is  to  so  thoroughly  incorporate 
the  ingredients  that  no  two  grains  of  sand  shall  lie  together  without 


30  MASONRY  CONSTRUCTION 

an  intervening  layer  or  film  of  cement.  To  accomplish  this  the 
cement  must  be  uniformly  distributed  through  the  sand  during  the 
dry  mixing. 

The  mixers  usually  fail  to  thoroughly  intermix  the  dry  cement 
and  sand,  and  to  lighten  the  labor  of  the  wet  mixing  they  will  give 
an  overdose  of  water. 

Packed  cement  when  measured  loose  increases  in  volume  to 
such  an  extent  that  a  nominal  1  to  3  mortar  is  easily  changed  to  an 
actual  1  to  4.  The  specifications  should  prescribe  the  manner  in 
which  the  materials  are  to  be  measured,  i.e.,  packed  or  loose. 

The  quantity  of  sand  will  also  vary  according  to  whether  it  is 
measured  in  a  wet  or  dry  condition,  packed  or  loose.  On  work  of 
sufficient  importance  to  justify  some  sacrifice  of  convenience  the 
sand  and  cement  should  be  proportioned  by  weight  instead  of  by 
volume. 

In  mixing  by  hand  a  platform  or  box  should  be  used;  the  sand 
and  cement  should  be  spread  in  layers  with  a  layer  of  sand  at  the 
bottom,  then  turned  and  mixed  with  shovels  until  a  thorough  incor- 
poration is  effected.  The  dry  mixture  should  then  be  spread  out, 
a  bowl-like  depression  formed  in  the  center  and  all  the  water  required 
poured  into  it.  The  dry  material  from  the  outside  of  the  basin  should 
be  thrown  in  until  the  water  is  taken  up  and  then  worked  into  a 
plastic  condition,  or  the  dry  mixture  may  be  shovelled  to  one  end  of 
the  box  and  the  water  poured  into  the  other  end.  The  mixture  of 
sand  and  cement  is  then  drawn  down  with  a  hoe,  small  quantities 
at  a  time,  and  mixed  with  the  water  until  enough  has  been  added 
to  make  a  good  stiff  mortar. 

In  order  to  secure  proper  manipulation  of  the  materials  on  the 
part  of  the  workmen  it  is  usual  to  require  that  the  whole  mass  shall 
be  turned  over  a  certain  number  of  times  with  the  shovels,  both  dry 
and  wet. 

The  mixing  wet  with  the  shovels  must  be  performed  quickly 
and  energetically.  The  paste  thus  made  should  be  vigorously  worked 
with  a  hoe  for  several  minutes  to  insure  an  even  mixture.  The 
mortar  should  then  leave  the  hoe  clean  when  drawn  out  of  it,  and 
very  little  should  stick  to  the  steel. 

A  large  quantity  of  cement  and  sand  should  not  be  mixed  dry 
and  left  to  stand  a  considerable  time  before  using,  as  the  moisture 


MASONRY  CONSTRUCTION  31 

in  the  sand  will  to  some  extent  act  upon  the  cement,  causing  a  partial 
setting. 

Upon  large  works  mechanical  mixers  are  frequently  employed 
with  the.  advantage  of  at  once  lessening  the  labor  of  manipulating 
the  material  and  insuring  good  work. 

Retempering  flortar.  Masons  very  frequently  mix  mortar  in 
considerable  quantities,  and  if  the  mass  becomes  stiffened  before 
being  used,  by  the  setting  of  the  cement,  add  water  and  work  it  again 
to  a  soft  or  plastic  condition.  After  this  second  tempering  the  cement 
is  much  less  active  than  at  first,  and  will  remain  for  a  longer  time  in 
a  workable  condition. 

This  practice  is  condemned  by  engineers,  and  is  not  usually 
allowed  in  good  engineering  construction.  Only  sufficient  quantity 
of  mortar  should  be  mixed  at  once  as  may  be  used  before  the  cement 
takes  the  initial  set.  Reject  all  mortar  that  has  set  before  being 
placed  in  the  w^ork. 

Freezing  of  flortar.  It  does  not  appear  that  common  lime 
mortar  is  seriously  injured  by  freezing,  provided  it  remains  frozen 
until  it  has  fully  set.  The  freezing  retards,  but  does  not  entirely 
suspend  the  setting.  Alternate  freezing  and  thawing  materially 
damages  the  strength  and  adhesion  of  lime  mortar. 

Although  the  strength  of  the  mortar  is  not  decreased  by  freezing, 
it  is  not  always  permissible  to  lay  masonry  during  freezing  weather; 
for  example,  if,  in  a  thin  wall,  the  mortar  freezes  before  setting  and 
afterwards  thaws  on  one  side  only,  the  wall  may  settle  injuriously. 

Mortar  composed  of  one  part  Portland  cement  and  three  parts 
sand  is  entirely  uninjured  by  freezing  and  thawing. 

Mortar  made  of  cements  of  the  Rosendale  type,  in  any  propor- 
tion, is  entirely  ruined  by  freezing  and  thawing. 

Mortar  made  of  overclayed  cement  (which  condition  is  indicated 
by  its  quicker  setting),  of  either  the  Portland  or  Rosendale  type, 
will  not  withstand  the  action  of  frost  as  well  as  one  containing  less 
clay,  for  .since  the  clay  absorbs  an  excess  of  water,  it  gives  an  increased 
effect  to  the  action  of  frost. 

In  making  cement  mortar  during  freezing  weather  it  is  cus- 
tomary to  add  salt  or  brine  to  the  water  with  which  it  is  mixed.  The 
ordinary  rule  is:  Dissolve  1  pound  of  salt  in  18  gallons  of  water 


QF  THE 

UNIVERSITY 

OF 


32 


MASONRY  CONSTRUCTION 


when  the  temperature  is  at  32°  F.,  and  add  1  ounce  of  salt  for  each 
degree  of  lower  temperature. 

The  use  of  salt,  and  more  especially  of  sea-water,  in  mortar  is 
objectionable  in  exposed  walls,  since  the  accompanying  salts  usually 
produce  efflorescence. 

The  practice  of  adding  hot  water  to  lime  mortar  during  freezing 
weather  is  undesirable.  When  the  very  best  results  are  sought  the 
brick  or  stone  should  be  warmed — enough  to  thaw  off  any  ice  upon 
the  surface  is  sufficient — before  being  laid.  They  may  be  warmed 
either  by  laying  them  on  a  furnace,  or  by  suspending  them  over  a 
slow  fire,  or  by  wetting  with  hot  water. 

TABLE  6. 

Amount  of  Cement  and  Sand   Required  for  One  Cubic  Yard  of 

flortar. 


Composition  of  mortar  by 
volumes. 


Cement.* 
Number  of  barrels. 


Cement. 

Sand. 

Portland  or 
Ulster  County 
Rosendale. 

» 

Western 
Koseudale. 

0 

7.14 

6.43 

1 

4.16 

3.71 

2 

2.85 

2.57 

3 

2.00 

1.80 

4 

1.70 

1.53 

5 

1.25 

1.13 

1 

6 

1.18 

1.06 

Cement.    Number  of  Pounds.t 

1 

0 

2675 

2140 

1 

1 

1440 

1150 

1 

2 

900 

720 

1 

3 

675 

540 

1 

4 

525 

420 

1 

5 

425 

340 

1 

0 

355 

285 

Sand. 
cubic.1  yards 


0.00 
0.58 
0.80 

0.90 
0.95 
0.97 
0.98 


0.00 
0,67 
0.84 
0.94 
0.9S 
0*99 
1.00 


*  Packed  cement  and  loose  sand. 
t  Loose  cement  and  loose  sand. 


MASONRY  CONSTRUCTION  33 

CONCRETE. 

Concrete  is  a  species  of  artificial  stone  composed  of  (1)  the 
matrix,  which  may  be  either  lime  or  cement  mortar,  usually  the  latter, 
and  (2)  the  aggregate,  which  may  be  any  hard  material,  as  gravel, 
shingle,  broken  stone,  shells,  brick,  slag,  etc. 

The  aggregate  should  be  of  different  sizes,  so  that  the  smaller 
shall  fit  into  the  voids  between  the  larger.  This  requires  less  mortar 
and  with  good  aggregate  gives  a  stronger  concrete.  Broken  stone 
is  the  most  common  aggregate. 

Gravel  and  shingle  should  be  screened  to  remove  the  larger-sized 
pebbles,  dirt,  and  vegetable  matter,  and  should  be  washed  if  they 
contain  silt  or  loam.  The  broken  stone  if  mixed  with  dust  or  dirt 
must  be  washed  before  .use. 

Strength  of  Concrete.  The  resistance  of  concrete  to  crush- 
ing ranges  from  about  600  to  1400  pounds  per  sq.  in.  It  depends 
upon  the  kind  and  amount  of  cement  and  upon  the  kind,  size,  and 
strength  of  the  aggregate.  The  transverse  strength  ranges  between 
50  and  400  pounds. 

Weight  of  Concrete.  A  cubic  yard  weighs  from  2,500  to 
3,000  pounds  according  to  its  composition. 

PROPORTIONS   OF   flATERIALS    FOR   CONCRETE. 

To  manufacture  one  cubic  yard  of  concrete  the  following  quan- 
tities of  materials  are  required : 

BROKEN-STONE-AND-GRAVEL  CONCRETE. 

Broken-stone  50%  of  its  bulk  voids 1  cubic  yard 

Gravel  to  fill  voids  in  the  stone .  .   J      " 

Sand  to  fill  voids  in  the  gravel J      " 

Cement  to  fill  voids  in  the  sand J      " 

BROKEN-STONE  CONCRETE. 

Broken  stone  50%  of  its  bulk  voids  ....  1  cubic  yard 

Sand  to  fill  voids  in  the  stone  .........  %      " 

Cement  to  fill  voids  in  the  sand J      " 

GRAVEL  CONCRETE. 

Gravel  J  of  its  bulk  voids 1  cubic  yard 

Sand  to  fill  voids  in  the  gravel J      " 

Cement  to  fill  voids  in  the  sand " 


34  MASONRY  CONSTRUCTION 

Concrete  composed  of  1  part  Rosendale  cement,  2  parts  of  sand, 
and  5  parts  of  broken  stone  requires: 

Broken  stone 0.92  cubic  yard 

Sand.  ......,.:..;.; 0.37     " 

Cement 1 . 43  barrels 

The  usual  proportions  of  the  materials  in  concrete  are: 
ROSENDALE  CEMENT  CONCRETE. 

Rosendale  cement 1  part 

Sand .... 2  parts 

Broken  stone 3  to  4     " 

PORTLAND  CEMENT  CONCRETE. 

Portland  cement 1  part 

Sand . . 2  to  3  parts 

Broken  stone  or  gravel 3  to  7     " 

To  make  100  cubic  feet  of  concrete  of  the  proportions  1  to  6  will 
require  5  bbl.  cement  (original  package)  and  4.4  yards  of  stone  and 
sand. 

flixing  Concrete.  The  concrete  may  be  mixed  by  hand  or 
machinery.  In  hand-mixing  the  cement  and  sand  are  mixed  dry. 
About  half  the  sand  to  be  used  in  a  batch  of  concrete  is  spread  evenly 
over  the  mortar-board,  then  the  dry  cement  is  spread  evenly  over 
the  sand,  and  then  the  remainder  of  the  sand  is  spread  on  top  of  the 
cement.  The  sand  and  cement  are  then  mixed  with  a  hoe  or  by 
turning  and  re-turning  with  a  shovel.  It  is  very  important  that  the 
sand  and  cement  be  thoroughly  mixed.  A  basin  is  then  formed  by 
drawing  the  mixed  sand  and  cement  to  the  outer  edges  of  the  board, 
and  the  whole  amount  of  water  required  is  poured  into  it.  The 
sand  and  cement  are  then  thrown  back  upon  the  water  and  thoroughly 
mixed  with  the  hoe  or  shovel  into  a  stiff  mortar  and  then  levelled  off. 
The  broken  stone  or  gravel  should  be  sprinkled  with  sufficient  water 
to  remove  all  dust  and  thoroughly  wet  the  entire  surface.  The 
amount  of  water  required  for  this  purpose  will  vary  considerably 
with  the  absorbent  power  of  the  stone  and  the  temperature  of  the  air. 
The  wet  stone  is  then  spread  evenly  over  the  top  of  the  mortar  and 
the  whole  mass  thoroughly  mixed  by  turning  over  with  the  shovel. 
Two,  three,  or  more  turnings  may  be  necessary.  It  should  be  turned 


MASONRY  CONSTRUCTION  35 

until  every  stone  is  coated  with  mortar,  and  the  entire  mass  presents 
the  uniform  color  of  the  cement,  and  the  mortar  and  stones  are  uni- 
formly distributed.  When  the  aggregate  consists  of  broken  brick 
or  other  porous  material  it  should  be  thoroughly  wetted  and  time 
allowed  for  absorption  previous  to  use;  otherwise  it  will  take  away 
part  of  the  water  necessary  to  effect  the  setting  of  the  cement. 

When  the  concrete  is  ready  for  use  it  should  be  quite  coherent 
and  capable  of  standing  at  a  steep  slope  without  the  water  running 
from  it. 

The  rules  and  the  practice  governing  the  mixing  of  concrete 
vary  as  widely  as  the  proportion  of  the  ingredients.  It  may  be  stated 
in  general  that  if  too  much  time  is  not  consumed  in  mixing  the  wet 
materials  a  good  result  can  be  obtained  by  any  of  the  many  ways 
practised,  if  only  the  mixing  is  thorough.  With  four  men  the  time 
required  for  mixing  one  cubic  yard  is  about  ten  minutes. 

Whatever  the  method  adopted  for  mixing  the  concrete,  it  is 
advisable  for  the  inspector  to  be  constantly  present  during  the  opera- 
tion, as  the  temptation  to  economize  on  the  cement  and  to  add  an 
excess  of  water  to  lighten  the  labor  of  mixing  is  very  great. 

Laying  Concrete.  Concrete  is  usually  deposited  in  layers, 
the  thickness  of  which  is  generally  stated  in  the  specifications  for 
the  particular  work  (the  thickness  varies  between  6  and  12  in.).  The 
concrete  must  be  carefully  deposited  in  place.  A  very  common 
practice  is  to  tip  it  from  a  height  of  several  feet  into  the  trench.  This 
process  is  objected  to  by  the  best  authorities  on  the  ground  that  the 
heavy  and  light  portions  separate  while  falling,  and  that  the  concrete 
is,  therefore,  not  uniform  throughout  its  mass. 

The  best  method  is  to  wheel  the  concrete  in  barrows,  imme- 
diately after  mixing,  to  the  place  where  it  is  to  be  laid,  gently  tipping 
or  sliding  it  into  position  and  at  once  ramming  it. 

The  ramming  should  be  done  before  the  cement  begins  to  set, 
and  should  be  continued  until  the  water  begins  to  ooze  out  upon 
the  upper  surface.  When  this  occurs  it  indicates  a  sufficient  degree 
of  compactness.  A  gelatinous  or  quicksand  condition  of  the  mass 
indicates  that  too  much  water  was  used  in  mixing.  Too  severe  or 
long-continued  pounding  injures  the  strength  by  forcing  the  stones 
to  the  bottom  of  the  layers  and  by  distributing  the  incipient  "set" 
of  the  cement. 


36  MASONRY  CONSTRUCTION 


The  rammers  need  not  be  very  heavy,  10  to  15  Ib.  will  be  suffi- 
cient. Square  ones  should  measure  from  0  to  8  in.  on  a  side  and 
round  ones  from  8  to  12  in.  in  diameter. 

After  each  layer  has  been  rammed  it  should  be  allowed  sufficient 
time  to  "set",  without  walking  on  it  or  in  other  ways  disturbing  it. 
If  successive  layers  are  to  be  laid  the  surface  of  the  one  already  set 
should  be  swept  clean,  wetted,  and  made  rough  by  means  of  a  pick 
for  the  reception  of  the  next  layer. 

Great  care  should  be  observed  in  joining  the  work  of  one  day 
to  that  of  the  next.  The  last  layer  should  be  thoroughly  compacted 
and  left  with  a  slight  excess  of  mortar.  It  should  be  finished  with 
a  level  surface,  and  when  partially  set  should  be  scratched  with  a 
pointed  stick  and  covered  with  planks,  canvas,  or  straw.  In  the 
morning,  immediately  before  the  application  of  the  next  layer,  the 
surface  should  be  swept  clean,  moistened  with  water,  and  painted 
with  a  wash  of  neat  cement  mixed  with  water  to  the  consistency  of 
cream.  This  should  be  put  on  in  excess  and  brushed  thoroughly 
back  and  forth  upon  the  surface  so  as  to  insure  a  close  contact 
therewith. 

Depositing  Concrete  Under  Water.  In  laying  concrete  under 
water  an  essential  requisite  is  that  the  materials  shall  not  fall. 
from  any  height  through  the  water,  but  be  deposited  in  the  allotted 
place  in  a  compact  mass;  otherwise  the  cement  will  be  separated 
from  the  other  ingredients  and  the  strength  of  the  work  be  seriously 
impaired.  If  the  concrete  is  allowed  to  fall  through  the  water  its 
ingredients  will  be  deposited  in  a  series,  the  heaviest — the  stone — at 
the  bottom,  and  the  lightest — the  cement — at  the  top.  A  fall  of  even 
one  foot  causes  an  appreciable  separation. 

A  common  method  of  depositing  concrete  under  water  is  to 
place  it  in  a  V-shaped  box  of  wood  or  plate  iron,  which  is  lowered 
to  the  bottom  with  a  crane.  The  box  is  so  constructed  that  on  reach- 
ing the  bottom  a  latch  operated  by  a  rope  reaching  to  the  surface 
can  be  drawn  out,  thus  permitting  one  of  the  sloping  sides  to  swing 
open  and  allow  the  concrete  to  fall  out.  The  box  is  then  raised 
and  refilled. 

A  long  box  or  tube,  called  a  tremie,  is  also  used.  It  consists 
of  a  tube  open  at  top  and  bottom  built  in  detachable  sections,  so 
that  the  length  may  be  adjusted  to  the  depth  of  water.  The  tube 


MASONRY  CONSTRUCTION  37 

; • . _____ 


is  suspended  from  a  crane  or  movable  frame  running  on  a  track,  by 
which  it  is  moved  about  as  the  work  progresses.  The  upper  end  is 
hopper-shaped,  and  is  kept  above  the  water;  the  lower  end  rests  on 
the  bottom.  The  tremie  is  rilled  in  the  beginning  by  placing  the 
lower  end  in  a  box  with  a  movable  bottom,  filling  the  tube,  lowering 
all  to  the  bottom,  and  then  detaching  the  bottom  of  the  box.  The 
tube  is  kept  full  of  concrete  by  more  being  thrown  in  at  the  top  as 
the  mass  issues  from  the  bottom. 

Concrete  is  also  successfully  deposited  under  water  by  enclosing 
it  in  paper  bags  and  lowering  or  sliding  them  down  a  chute  into 
place.  The  bags  get  wet  and  the  pressure  of  the  concrete  soon  bursts 
them,  thus  allowing  the  concrete  to  unite  into  a  solid  mass.  Concrete 
is  also  sometimes  deposited  under  water  by  enclosing  it  in  open-cloth 
bags,  the  cement  oozing  through  the  meshes  sufficiently  to  unite  the 
whole  into  a  single  mass. 

Concrete  should  not  be  deposited  in  running  water  unless  pro- 
tected by  one  or  other  of  the  above-described  methods;  otherwise 
the  cement  will  be  washed  out. 

Concrete  deposited  under  water  should  not  be  rammed,  but  if 
necessary  may  be  levelled  with  a  rake  or  other  suitable  tool  imme- 
diately after  being  deposited. 

When  concrete  is  deposited  in  water  a  pulpy,  gelatinous  fluid 
is  washed  from  the  cement  and  rises  to  the  surface.  This  causes 
the  water  to  assume  a  milky  hue.  The  French  engineers  apply  the 
term  laitance  to  this  substance.  It  is  more  abundant  in  salt  water 
than  in  fresh.  The  theory  of  its  formation  is  that  the  immersed 
concrete  gives  up  to  the  water,  free  caustic  lime,  which  precipitates 
magnesia  in  a  light  and  spongy  form.  This  precipitate  sets  very 
slowly,  and  sometimes  scarcely  at  all,  and  its  interposition  between 
the  layers  of  concrete  forms  strata  of  separation.  The  proportion 
of  laitance  is  greatly  diminished  by  using  large  immersion-boxes, 
or  a  tremie,  or  paper  or  cloth  bags. 

Asphaltic  Concrete  is  composed  of  asphaltic  mortar  and 
broken  stone  in  the  proportion  of  5  parts  of  stone  to  3  parts  of  mortar. 
The  stone  is  heated  to  a  temperature  of  about  250°  F.  and  added  to 
the  hot  mortar.  The  mixing  is  usually  performed  in  a  mechanical 
mixer. 


MASONRY  CONSTRUCTION 


The  material  is  laid  hot  and  rammed  until  the  surface  is  smooth. 
Care  is  required  that  the  materials  are  properly  heated,  that  the 
place  where  it  is  to  be  laid  is  absolutely  dry  and  that  the  ramming 
is  done  before  it  chills  or  becomes  set.  The  rammers  should  be  heated 
in  a  portable  fire. 

CLAY   PUDDLE. 

Clay  puddle  is  a  mass  of  clay  and  sand  worked  into  a  plastic 
condition  with  water.  It  is  used  for  filling  coffer-dams,  for  making 
embankments  and  reservoirs  water-tight,  and  for  protecting  masonry 
against  the  penetration  of  water  from  behind. 

Quality  of  Clay.  The  clays  best  suited  for  puddle  are  opaque, 
and  not  crystallized,  should  exhibit  a  dull  earthy  fracture,  exhale 
when  breathed  upon  a  peculiar  faint  odor  termed  "argillaceous," 
should  be  unctuous  to  the  touch,  free  from  gritty  matter,  and  form 
a  plastic  paste  with  water. 

The  important  properties  of  clay  for  making  good  puddle  are 
its  tenacity  or  cohesion  and  its  power  of  retaining  water.  The  tenac- 
ity of  a  clay  may  be  tested  by  working  up  a  small  quantity  with  water 
into  a  thoroughly  plastic  condition,  and  forming  it  by  hand  into  a 
roll  about  1  to  H  inches  in  diameter  by  10  or  12  inches  in  length. 
If  such  a  roll  is  sufficiently  cohesive  not  to  break  on  being  suspended 
by  one  end  while  wet  the  tenacity  of  the  material  is  ample. 

To  test  its  power  of  retaining  water  one  to  two  cubic  yards 
should  be  worked  with  water  to  a  compact  homogeneous  plastic 
condition,  and  then  a  hollow  should  be  formed  in  the  center  of  the 
mass  capable  of  holding  four  or  five  gallons  of  water.  After  filling 
the  hollow  with  water  it  should  be  covered  over  to  prevent  evaporation 
and  left  for  about  24  hours,  when  its  capability  of  holding  water  will 
be  indicated  by  the  presence  or  absence  of  water  in  the  hollow. 

The  clay  should  be  freed  from  large  stones  and  vegetable  matter, 
and  just  sufficient  sand  and  water  added  to  make  a  homogeneous 
mass.  If  there  is  too  little  sand  the  puddle  will  crack  by  shrinkage 
in  drying,  and  if  too  much  it  will  be  permeable. 

Puddling.  The  operation  of  puddling  consists  in  chopping 
the  clay  in  layers  of  about  3  inches  thick  with  spades,  aided  by  the 
addition  of  sufficient  water  to  reduce  it  to  a  pasty  condition.  After 


MASONRY  CONSTRUCTION  39 

each  chop  and  before  withdrawing  the  spade  it  should  be  given  a 
lunging  motion  so  as  to  permit  the  water  to  pass  through. 

The  spade  should  "pass  through  the  upper  layer  into  the  lower 
layer  so  as  to  cause  the  layers  to  bond  together. 

The  test  For  thorough  puddling  is  that  the  spade  will  pass  through 
the  layer  with  ease,  which  it  will  not  do  if  there  are  any  dry  hard 
lumps. 

Sometimes  in  place  of  spades,  harrows  are  used,  each  layer  of 
clay  being  thoroughly  harrowed  aided  by  water  and  then  rolled  with 
a  grooved  roller  to  compact  it. 

The  finished  puddle  should  not  be  exposed  to  the  drying  action 
of  the  air,  but  should  be  covered  with  a  layer  of  dry  clay  or  sand. 

FOUNDATIONS. 

The  foundation  is  the  most  critical  part  of  a  masonry  structure. 
The  failures  of  masonry  work  due  to  faulty  workmanship  or  to  an 
insufficient  thickness  of  the  walls  are  rare  in  comparison  with  those 
due  to  defective  foundations.  When  it  is  necessary,  as  so  frequently 
it  is  at  the  present  day,  to  erect  gigantic  edifices — as  high  buildings 
or  long-span  bridges — on  weak  and  treacherous  soils,  the  highest 
constructive  skill  is  required  to  supplement  the  weakness  of  the 
natural  foundation  by  such  artificial  preparations  as  will  enable  it 
to  sustain  the  load  with  safety. 

Natural  Foundations.  The  soils  comprised  under  this  head 
may  be  divided  into  two  classes.  (1)  Those  whose  stability  is  not 
affected  by  water,  and  which  are  firm  enough  to  support  the  structure, 
such  as  rock,  compact  gravels,  and  hard  clay,  and  (2)  soils  which  are 
firm  enough  to  support  the  weight  of  the  structure,  but  whose  stability 
is  affected  by  water,  such  as  loose  gravels,  sand,  clay  and  loam. 

Foundations  on  Rock.  To  prepare  a  rock  foundation,  all 
that  is  generally  necessary  is  to  cut  away  the  loose  and  decayed  por- 
tions and  to  dre'ss  the  surface  so  exposed  to  a  plane  as  nearly  perpen- 
dicular to  the  direction  of  the  pressure  as  practicable;  or,  if  the  rock 
forms  an  inclined  plane,  to  cut  a  series  of  plane  surfaces,  like  those 
of  steps,  for  the  walls  to  rest  upon.  If  there  are  any  fissures  in  the 
rock  they  should  be  filled  with  concrete. 

Foundations  on  Gravel,  Etc.  In  dealing  with  soils  of  this 
kind  usually  nothing  more  is  required  than  to  cover  them  with  a 


40 


MASONRY  CONSTRUCTION 


layer  of  concrete  of  width  and  depth  sufficient  to  distribute  the  weight 
properly. 

Foundations  on  Sand. '  Sand  is  almost  incompressible  so  long 
as  it  is  not  allowed  to  spread  out  laterally,  but  as  it  has  no  cohesion, 
and  acts  like  a  fluid  when  exposed  to  running  water,  it  must  be  treated 
with  great  caution. 

Foundations  on  Clay.  Clay  is  much  affected  by  the  action 
of  water,  and  hence  the  ground  should  be  well  drained  before  the 
work  is  begun,  and  the  trenches  so  arranged  that  water  does  not 
remain  in  them.  In  general,  the  less  a  soil  of  this  kind  is  exposed 
to  the  action  of  the  air,  and  the  sooner  it  is  protected  from  exposure, 
the  better  for  the  work.  The  top  of  the  footings  must  be  carried 
below  the  frost  line  to  prevent  heaving,  and  for  the  same  reason  the 
outside  face  of  the  wall  should  be  built  with  a  slight  batter  and  per- 
fectly smooth.  The  frost  line  attains  a  depth  of  six  feet  in  some  of 
the  northern  states. 

The  bearing  power  of  clay  and  loamy  soils  may  be  greatly  in- 
creased: (1)  By  increasing  the  depth.  (2)  By  drainage.  This 

may  be  accomplished  by  a  cover- 
ing of  gravel  or  sand,  the  thick- 
ness depending  upon  the  plas- 
ticity of  the  soil,  and  by  surround- 
ing the  foundation  walls  with  a 
tile  drain  as  in  Fig.  5.  If  springs 
are  encountered  the  water  may 
be  excluded  by  sheet  pilings, 
puddling  or  plugging  the  spring 
with  concrete.  (3)  By  consoli- 
dating the  soil.  This  ni'iy  be 
done  by  driving  short  piles  close 
together,  or  by  driving  piles,  then 
withdrawing  them  an-1  filling  the 
space  immediately  with  damp  sand  well  rammed.  If  the  soil  is  very 
loose  and  wet,  sand  will  not  be  effective,  and  concrete  will  be  found 
more  satisfactory. 

Artificial  Foundations.  When  the  ground  in  its  natural 
state  is  too  soft  to  bear  the  weight  of  the  proposed  structure,  recourse 
must  be  had  to  artificial  means  of  support,  and,  in  doing  this,  whai- 


Fig.  5.    Drainage  of  Foundation  Walls. 


MASONRY  CONSTRUCTION  41 

ever  mode  of  construction  is  adopted,  the  principle  must  always  be 
that  of  extending  the  bearing  surface  as  much  as  possible. 

Foundations  on  Mud,  silt,  marshy  or  compressible  soils  are 
generally  formed  in  one  of  three  ways:  (1)  By  driving  piles  in  which 
the  footings  are  supported.  (2)  By  spreading  the  footings  either 
by  layers  of  timber,  steel  beams,  or  concrete,  or  a  combination  of 
either.  (3)  By  sinking  caissons  of  iron  or  steel,  excavating  the  soil 
from  the  interior,  and  filling  with  concrete. 

Foundations  in  Water  are  formed  in  several  ways:  (1) 
Wholly  of  piles.  (2)  Solid  foundations  laid  upon  the  surface  of 
the  ground  by  means  of  cribs,  caissons,  or  piles,  and  grillage.  (3) 
Solid  foundations  laid  60/010  the  surface,  the  ground  being  made  dry 
by  cofferdams  or  caissons.  (4)  Where  the  site  is  perfectly  firm, 
and  there  is  no  danger  of  the  work  being  undermined  by  scour, 
foundations  are  started  on  the  surface,  the  inequalities  being  first 
removed  by  blasting  or  dredging.  The  simplest  foundation  of  this 
class  is  called  "Random"  work  or  Pierre  perdue.  It  is  formed  by 
throwing  large  masses  of  stone  upon  the  site  until  the  mass  reaches 
the  surface  of  the  water,  above  which  the  work  can  be  carried  on  in 
the  usual  manner.  Large  rectangular  blocks  of  stone  or  concrete 
are  also  used,  the  bottom  being  first  simply  leveled  and  the  blocks 
carefully  lowered  into  place. 

PILE  FOUNDATIONS. 

Timber  Piles  are  generally  round,  the  diameter  at  the  butt 
varying  from  9  to  18  inches.  They  should  be  straight-grained  and 
as  free  from  knots  as  possible.  The  variety  of  timber  is  usually 
selected  according  to  the  character  of  the  soil.  Where  the  piles 
will  be  always  under  water  and  where  the  soil  is  soft,  spruce  and  hem- 
locks are  used.  For  firm  soils  the  hard  pines,  fir,  elm  and  beech  are 
preferable.  Where  the  piles  will  be  alternately  wet  and  dry,  white 
or  black  oak  and  yellow  pine  are  used.  Piles  exposed  to  tide  water 
are  generally  driven  with  the  bark  on.  It  is  customary  to  fix  an  iron 
hoop  to  the  heads  of  piles  to  prevent  their  splitting,  and  also  to  have 
them  shod  with  either  cast-  or  wrought-iron  shoes. 

Timber  piles  when  partly  above  and  partly  under  water,  decay 
rapidly  at  the  water  line  owing  to  the  alternations  of  dryness  and 
moisture.  In  tidal  waters  they  are  destroyed  by  the  marine  worm 


42 


MASONRY  CONSTRUCTION 


called  the  "teredo  navalis."  To  preserve  timber  in  such  situations 
several  processes  are  in  use.  The  one  most  extensively  employed 
is  known  as  "  creosoting, "  which  consists  of  injecting  creosote  or 

dead  oil  of  coal  tar  into 
the  pores  of  the  timber. 
The  frame  of  timbers 
placed  on  the  top  of  the 
piles  is  called  the  grillage. 
The  piles  are  sawed  off 
square  below  low  water, 
a  timber  called  a  cap  is 
placed  on  the  ends  of 
the  piles  and  fastened 
with  drift  bolts,  and 


Fig.  6.    Timber  Pile  Foundation. 


transverse  timbers  called 
strips  are  placed  on  the 

caps  and  drift-bolted  to  them.  As  many  courses  as  necessary  may  be 
added,  each  at  right  angles  to  the  one  below  it,  the  top  courses  being 
either  laid  close  together  to  form  a  floor  or  else  covered  with  heavy 
plank  to  receive  the  masonry. 

In  some  cases  the  grillage  is  omitted,  a  layer  of  concrete  being 
used  instead,  with  the  heads  of  the  piles  embedded  therein,  as  shown 
in  Fig.  7.     The  name  gril- 
lage   is   also    applied   to  a  '^ ea-s^ 

combination  of  steel  beams 
and  concrete. 

Iron  and  Steel  Piles. 
Cast  iron,  wrought  iron, 
and  steel  are  employed  for 
ordinary  bearing  piles,  sheet 
piles,  and  for  cylinders. 
Iron  cylinders  are  usually 
.sunk  either  by  dredging  the 
soil  from  the  inside  or  by 
the  pneumatic  process. 

Cast-iron  piles  are  used 
as  substitutes  for  wooden  ones.     Lugs  or  flanges  are  usually  cast  on 
the  sides  of  die  piles,  to  which  bracing  may  be  attached  for  securing 


r 


Fig.  7.    Timber  Piles,  Concrete  Capping,  and 
I-Beam  Grillage. 


MASONRY  CONSTRUCTION 


them  in  position.  A  wooden  block  is  laid  on  top  of  the  pile  to 
receive  the  blows  of  the  hammer,  and  after  being  driven  a  cap  with 
a  socket  in  its  lower  side  is  placed  upon  the  pile  to  receive  the  load. 
Solid  rolled-steel  piles  are  driven  in  the  same  manner  as  timber 
piles,  either  with  a  hammer,  machine  or  water-jet. 

Screw  Piles  are  piles  which  are  screwed  into 
the  stratum  in  which  they  are  to  stand.  They 
are  ordinary  piles  of  timber  or  iron  (the  latter 
usually  hollow),  to  the  bottom  of  which  a  screw  ' 
disk,  consisting  of  a  single  turn  of  the  spiral,  similar 
to  the  bottom  turn  of  an  auger,  is  fastened  by 
bolts  or  pins.  Instead  of  driving  these  piles  into 
the  ground  they  are  forced  in  by  turning  with 
levers  or  machinery  suitable  for  the  purpose. 
The  screw  disks  vary  in  diameter  from  1  to  6 
feet.  The  water  jet  is  sometimes  employed  by 
applying  it  to  the  under,  upper,  or  both  sides  of 
the  disk  for  the  purpose  of  reducing  the  resistance. 

Concrete  Piles.  Two  methods  of  forming 
these  piles  are  in  use.  (1)  The  piles  are  made 
in  moulds  and  carried  to  the  place  of  use  and 
driven  in'  the  same  manner  as  timber  piles.  (2) 
Holes  are  made  in  the  ground  and  rilled  with 
concrete. 

Moulded  Concrete  Piles.  Fig.  8  shows  the 
moulded  pile.  This  pile  is  made  in  moulds  and 
contains  four  vertical  rods  a  at  the  corners,  the 
rods  are  stayed  by  loops  or  hooks  b  of  large  wire 
sprung  into  place  across  the  sides  of  the  pile  and 
held  transversely  by  horizontal  strips  of  thin 
metal.  The  feet  of  the  piles  are  either  wedge  Section  A-B 

shaped  or  pyramidal  and  are  protected  by  cast-  Fig.  8.  Moulded  con- 
iron  points  with  side  plates  which  turn  in  at  c  to 
lock  with  the  concrete.  The  upper  ends  of  the  piles  are  shouldered  in 
to  give  clearance  for  the  driving  cap  d.  This  is  a  cast  steel  hood 
which  fits  loosely  around  the  neck  of  the  pile,  and  is  filled  with  dry 
sand  or  a  bag  of  sawdust  df  retained  by  a  clay  ring  and  hemp  jacket 
e  at  the  bottom  of  the  cap. 


44 


MASONRY  CONSTRUCTION 


Fig.  y. 


OlA 

Concrete  Pile. 


The  sand  absorbs  the  impact  of  the  hammer  so  as  to  permit 
the  piles  to  be  driven  safely,  and  it  raises  the  hood  sufficiently  above 
the  top  of  the  pile  to  permit  the  reinforcement  rods  to  extend  beyond 
the  concrete  for  connection  with  the  superstructure. 

Concrete  Piles  Formed  in  Place.  Fig.  9  shows  this  type 
of  pile.  The  hole  is  made  by  driving  with  an  ordinary  pile-driving 
apparatus,  a  sheet  steel  tube  tapering  from  20  inches 

at  the  top  to  6  inches  at 
the  bottom,  the  tube  is 
driven  by  means  of  a  col- 
lapsible core  which  is  with- 
drawn. When  the  desired 
depth  is  reached,  the  tube 
is  then  filled  with  concrete. 
Fig.  10  shows  another 
method  of  forming  this  type 
of  pile.  A  sheet  steel  shell 
is  formed  by  telescopic  sec- 
tions, each  section  is  8  ft. 
long  and  has  at  its  upper 
end  projections  which  en- 
gage with  projections  on 
the  lower  end  of  the  next 
section.  To  the  bottom  sec- 
tion is  attached  a  cast  iron 
point  with  a  f-in.  jet  hole 
or  nozzle,  to  which  is  fitted 
a  2J-in.  pipe,  this  pipe  is 
held  in  place  by  spreaders  and  remains  in  place  in  the  finished  pile, 
to  which  it  adds  lateral  strength.  The  shell  is  sunk  by  water  jet  and 

filled  with  concrete. 

PILE-DRIVING. 

Timber  piles  are  driven  either  point  or  butt  end  down;  the  latter 
is  considered  the  better  method.  When  piles  are  directed  to  be 
sharpened  the  points  should  have  a  length  of  from  one  and  a  half 
times  to  twice  the  diameter. 

To  prevent  the  head  of  the  pile  from  being  broomed  or  split 
by  the  blows  of  the  driving-ram  it  is  bound  with  a  wrought-iron 


Fig.  10.    Con- 
crete Pile. 


MASONRY  CONSTRUCTION  45 


hoop,  2  to  3  inches  wide  and  J  to  1  inch  thick.  Instead  of  the  wrought- 
iron  band  a  cast-iron  cap  is  sometimes  used.  It  consists  of  a  block 
with  a  tapering  recess  above  and  below,  the  chamfered  head  of  the 
pile  fitting  into  the  one  below,  and  a  cushion  piece  of  hard  wood  upon 
which  the  hammer  falls  fitting  into  the  one  above. 

When  brooming  occurs  the  broomed  part  should  be  cut  off, 
because  a  broomed  head  cushions  the  blow  and  dissipates  it  without 
any  useful  effect.  Piles  that  split  or  broom  excessively  or  are  other- 
wise injured  during  the  driving  must  be  drawn  out. 

Bouncing  of  the  hammer  occurs  when  the  pile  refuses  to  drive 
further,  or  it  may  be  caused  by  the  hammer  being  too  light,  or  its 
striking  velocity  being  too  great,  or  both.  The  remedy  for  bouncing 
is  to  diminish  the  fall. 

Excessive  hammering  on  piles  which  refuse  to  move  should  be 
avoided,  as  they  are  liable  to  be  crippled,  split,  or  broken  below  the 
ground.  Such  injury  will  pass  unnoticed  and  may  be  the  cause  of 
future  failure. 

As  a  general  rule,  a  heavy  hammer  with  a  low  fall  drives  more 
satisfactorily  than  a  light  one  with  a  high  fall.  More  blows  can  be 
made  in  the  same  time  with  a  low  fall,  and  this  gives  less  time  for 
the  soil  to  compact  itself  around  the  piles  between  the  blows.  At 
times  a  pile  may  resist  the  hammer  after  sinking  some  distance,  but 
start  again  after  a  short  rest;  or  it  may  refuse  a  heavy -hammer  and 
start  under  a  light  one.  It  may  drive  slowly  at  first,  and  more 
rapidly  afterwards,  from  causes  difficult  to  discover. 

The  driving  of  a  pile  sometimes  causes  adjacent  ones  previously 
driven  to  spring  upwards  several  feet.  The  driving  of  piles  in  soft 
ground  or  mud  will  generally  cause  adjacent  ones  previously  driven 
to  lean  outwards  unless  means  of  prevention  be  taken. 

A  pile  may  rest  upon  rock  and  yet  be  very  weak,  for  if  driven 
through  very  soft  soil  all  the  pressure  is  borne  by  the  sharp  point,  and 
the  pile  becomes  merely  a  column  in  a  worse  condition  than  a  pillar 
with  one  rounded  end.  In  such  soils  the  piles  need  very  little  sharp- 
ening; indeed,  they  had  better  be  driven  butt  end  down  without  any 
point.  Solid  metal  piles  are  usually  of  uniform  diameter  and  are 
driven  with  either  blunt  or  sharpened  points. 

Piles  are  driven  by  machines  called  pile  drivers.  A  pile  driver 
consists  essentially  of  two  upright  guides  or  leads,  often  of  great 


46  MASONRY  CONSTRUCTION 

height,  erected  upon  a  platform,  or  on  a  barge  when  used  in  water. 
These  guides  serve  to  hold  the  pile  vertical  while  being  driven,  and 
also  hold  and  guide  the  hammer  used  in  driving.  This  is  a  block 
of  iron  called  a  ram,  monkey,  or  hammer,  weighing  anywhere  from 
800  to  4,000  pounds,  usually  about  2,000  to  3,000  pounds.  The 
accessories  are  a  hoisting  engine  for  raising  the  hammer  and  the 
devices  for  allowing  it  to  drop  freely  on  the  heads  of  the  piles. 

The  steam  hammer  is  also  employed  for  driving  piles,  and  has 
certain  advantages  over  the  ordinary  form,  the  chief  of  which  lies 
in  the  great  rapidity  with  which  the  blows  follow  one  another,  allow- 
ing no  time  for  the  disturbed  earth,  sand,  etc.,  to  recompact  itself 
around  the  sides  and  under  the  foot  of  the  pile.  It  is  less  liable  than 
other  methods  to  split  and  broom  the  piles,  so  that  these  may  be  of 
softer  and  cheaper  wood,  and  the  piles  are  not  so  liable  to  " dodge" 
or  get  out  of  line. 

When  piles  have  to  be  driven  below  the  end  of  the  leaders  of 
the  pile  driver  a  follower  is  used.  This  is  made  from  a  pile  of  suita- 
ble length  placed  on  top  of  the  pile  to  be  driven.  To  prevent  its 
bouncing  off  caps  of  cast  iron  are  used,  one  end  being  bolted  to  the 
follower  and  the  other  end  fitting  over  the  head  of  the  pile. 

Piles  are  also  driven  by  the  "water  jet."  This  process  consists 
of  an  iron  pipe  fastened  by  staples  to  the  side  of  the  pile,  its  lower  end 
placed  near  the  point  of  the  pile  and  its  upper  end  connected  by  a 
hose  to  a  force  pump.  The  pile  can  be  sunk  through  almost  any 
material,  except  hardpan  and  rock,  by  forcing  water  through  the 
pipe.  It  seems  to  make  very  little  difference,  either  in  the  rapidity 
of  sinking  or  in  the  accuracy  with  which  the  pile  preserves  its  position, 
whether  the  nozzle  is  exactly  under  the  middle  of  the  pile  or  not. 

The  efficiency  of  the  jet  depends  upon  the  increased  fluidity 
given  the  material  into  which  the  piles  are  sunk,  the  actual  displace- 
ment of  material  being  small.  Hence  the  efficiency  of  the  jet  is 
greatest  in  clear  sand,  mud,  or  soft  clay.  In  gravel  or  in  sand  con- 
taining a  large  percentage  of  gravel,  or  in  hard  clay  the  jet  is  almost 
useless.  For  these  reasons  the  engine,  pump,  hose,  and  nozzle 
should  be  arranged  to  deliver  large  quantities  of  water  with  a  moder- 
ate force  rather  than  smaller  quantities  with  high  initial  velocity. 
In  gravel,  or  in  sand  containing  gravel,  some  benefit  might  result  from 
a  velocity  sufficient  to  displace  the  pebbles  and  drive  them  from  the 


MASONRY  CONSTRUCTION 


47 


vicinity  of  the  pile.  The  error  most  frequently  made  in  the  applica- 
tion of  the  water  jet  is  in  using  pumps  with  insufficient  capacity. 

The  approximate  volume  of  water  required  per  minute,  per 
inch  of  average  diameter  of  pile,  for  penetrations  under  40  feet  is 
16  gallons;  for  greater  depths  the  increase  in  the  volume  of  water 
is  approximately  at  the  rate  of  4  gallons  per  inch-  of  diameter  of  pile 
per  minute,  for  each  additional  10  feet  of  penetration. 

The  number  and  size  of  pipes  required  for  various  depths  are 
about  as  follows: 

TABLE  7. 


Depth  of 
penetration, 

feet. 

Diameter  of 
pipe,  inches. 

Number  of 
pipes. 

Diameter 
of  nozzle, 
inches. 

20 

2 

1 

i 

30 

2$ 

1 

it 

40 

2* 

2 

it 

50 

2* 

2 

i 

60 

2^ 

2 

I 

When  the  descent  of  the  pile  becomes  slow,  or  it  sticks  or  "  brings 
up "  in  some  tenacious  material,  it  can  usually  be  started  by  striking 
a  few  blows  with  the  pile-driving  hammer,  or  by  raising  the  pile  about 
6  inches  and  allowing  it  to  drop  suddenly,  with  the  jet  in  operation. 
By  repeating  the  operation  as  rapidly  as  possible  the  obstruction  will 
generally  be  overcome. 

It  is  an  advantage  to  use  an  ordinary  pile-driving  machine  for 
sinking  piles  with  the  water  jet.  The  hammer  being  allowed  to  rest 
upon  the  head  of  the  pile  aids  in  accelerating  the  descent,  and  light 
blows  can  be  struck  as  often  as  may  appear  necessary.  The  effi- 
ciency of  the  jet  can  also  be  greatly  increased  by  bringing  the  weight 
of  the  pontoon  upon  which  the  machinery  is  placed  to  bear  upon 
the  pile  by  means  of  a  block  and  tackle. 

Splicing  Piles.  It  frequently  happens  in  driving  piles  in 
swampy  places,  for  false  works,  etc.,  that  a  single  pile  is  not  long 
enough,  in  which  case  two  are  spliced  together.  A  common  method 
of  doing  this  is  as  follows.  After  the  first  pile  is  driven  its  head  is 
cut  off  square,  a  hole  2  inches  in  diameter  and  12  inches  deep  is 


48 


MASONRY  CONSTRUCTION 


bored  in  its  head,  and  an  oak  treenail  or  dowel-pin  23  inches  long 
is  driven  into  the  hole;  another  pile  similarly  squared  and  bored  is 
placed  upon  the  lower  pile,  and  the  driving  continued.  Spliced  in 
this  way  the  pile  is  deficient  in  lateral  stiffness,  and  the  upper  section 
is  liable  to  bounce  off  while  driving.  It  is  better  to  reinforce  the 
splice  by  flattening  the  sides  of  the  piles  and  nailing  on  with,  say,  8- 
inch  spikes  four  or  more  pieces  2  or  3  inches  thick,  4  or  5  inches  wide, 
and  4  to  6  feet  long. 

CONCRETE  WITH  STEEL  BEAHS. 

The  foundation  is  prepared  by  first  laying  a  bed  of  concrete 
to  a  depth  of  from  4  to  12  inches  and  then  placing  upon  it  a  row  of 


•bib'  IrPlaned  loiat. 

J 


Fig.  11.    Concrete,  and  Steel  I-Beams. 


I-beams  at  right  angles  to  the  face  of  the  wall.  In  the  case  of  heavy 
piers,  the  beams  may  be  crossed  in  two  directions.  Their  distance 
apart,  from  center  to  center,  may  vary  from  9  to  24  inches,  according 


MASONRY  CONSTRUCTION 


to  circumstances,  i.e.,  length  of  their  projection  beyond  the  masonry, 
thickness  of  concrete,  estimated  pressure  per  square  foot,  etc.  They 
should  be  placed  far  enough  apart  to  permit  the  introduction  of  the 
concrete  filling  and  its  proper  tamping. 

Hollow  Cylinders  of  cast  iron  or  plate  steel,  commonly  called 
caissons,  are  frequently  used  with  advantage.  The  cylinders  are 
made  in  short  lengths  with  internal  flanges  and  are  bolted  together 
as  each  preceding  length  is  lowered.  They  are  sunk  by  excavating 
the  natural  soil  from  the  interior.  When  the  stratum  on  which  they 
are  to  rest  has  been  reached  they  are  filled  with  concrete. 

Cofferdams.  There  are  many  circumstances  under  which  it 
becomes  necessary  to  expose  the  bottom  and  have  it  dry  before 
commencing  operations.  This  is  done  by  enclosing  the  site  of  the 
foundation  with  a  wrater-tight  wall.  The  great  difficulties  in  the 
construction  of  a  cofferdam  in  deep  water  are,  first,  to  keep  it  water- 


Fig.  12.    Cofferdam, 

tight,  and,  second,  to  support  the  sides  against  the  pressure  of  the 
water  outside.  Fig.  12  shows  the  simplest  form;  it  consists  of  two 
rows  of  piles  driven  closely  and  filled  with  clay  puddle.  In  shallow 
water  and  on  land  sheet  piling  is  sometimes  sufficient. 

Sheet  Piles  are  flat  piles,  usually  of  plank,  either  tongued  and 
grooved  or  grooved  only,  into  which  a  strip  of  tongue  is  driven;  or 
they  may  be  of  squared  timber,  in  which  case  they  are  called  "close 
piles,"  or  of  sheet  iron.  The  timber  ones  are  of  any  breadth  that 
can  be  procured,  and  from  2  to  10  inches  thick,  and  are  shaped  at 
the  lower  end  to  an  edge  wholly  from  one  side ;  this  point  being 
placed  next  to  the  last  pile  driven  tends  to  crowd  them  together  and 


50 


MASONRY  CONSTRUCTION 


make  tighter  joints  (the  angle  formed  at  the  point  should  be  30°). 
In  stony  ground  they  are  shod  with  iron. 

When  a  space  is  to  be  enclosed  with  sheet  piling  two  rows  of 
guide  piles  are  first  driven  at  regular  intervals  of  from  6  to  10  feet, 
and  to  opposite  sides  of  these  near  the  top  are  notched  or  bolted  a 
pair  of  parallel  string  pieces  or  "wales,  "  from  5  to  10  inches  square, 
so  fastened  to  the  guide  piles  as  to  leave  between  the  wales  equal  to  the 
thickness  of  the  sheet  piles. 

If  the  sheeting  is  to  stand  more  than  8  or  10  feet  above  the  ground, 
a  second  pair  of  wales  is  required  near  the  level  of  the  ground.  The 
sheet  piles  are  driven  between  the  wales,  working  from  each  end 
towards  the  middle  of  the  space  between  a  pair  of  guide  piles,  so  that 
the  la^t  or  central  pile  acts  as  a  wedge  to  tighten  the  whole. 

Sheet  piles  are  driven  either  by  mauls  wielded  by  men  or  by  a 
pile-driving  machine.  Ordinary  planks  are  also  used  for  sheet 


Fig.  13.    Sheet  Piling. 

piling,  being  driven  with  a  lap;  such  piling  is  designated  as  "single 
lap,"  "double  lap,"  and  "triple  lap."  The  latter  is  also  known  as 
the  "Wakefield"  triple-lap  sheet  piling,  shown  in  Fig.  13. 

Cribs  are  boxes  constructed  of  round  or  square  timber,  divided 
by  partitions  of  solid  timber  into  square  or  rectangular  cells.  The 
cells  are  floored  with  planks,  placed  a  little  above  the  lower  edge  so 
as  not  to  prevent  the  crib  from  settling  slightly  into  the  soil,  and  thus 
coming  to  a  full  bearing  on  the  bottom.  After  it  has  been  sunk  the 
cells  are  filled  with  sand  and  stone.  On  uneven  rock  bottom  it  may 
be  necessary  to  scribe  the  bottom  of  the  crib  to  fit  the  rock.  In  some 
cases  rip-rap  is  deposited  outside  around  the  crib  to  prevent  under- 


MASONRY  CONSTRUCTION 


51 


mining  by  the  current.  A  crib  with  only  an  outside  row  of  cells  for 
sinking  it  is  sometimes  used,  with  an  interior  chamber  in  which  con- 
crete is  laid  under  water  and  the  masonry  started  thereon.  Cribs 
are  sometimes  sunk  into  plac*?  and  then  piles  are  driven  in  the  cells, 
which  are  afterward  filled  with  concrete  or  broken  stone.  The  masonry 
may  then  rest  on  the  piles  only, 
which  in  turn  will  be  protected  by 
the  crib.  If  the  bottom  is  liable 
to  scour,  sheet  piles  or  rip-rap 
may  be  placed  outside  around  the 
base  of  the  crib.  Cribs  with 
only  an  outer  row  of  cells  for 
puddling  may  be  used  as  a  coffer- 
dam, the  joints  between  the  outer 
timbers  being  well  calked,  and 
care  taken  by  means  of  outside 
pile  planks  to  prevent  water  from 
entering  beneath  it. 

Caissons  are  of  two  forms, 
the  " erect"  or  "open"  and  the 
"inverted."  The  former  is  a 
strong  water-tight  timber  box, 
which  is  floated  over  the  site  of 
the  work,  and  being  kept  in  place 


by  guide  piles,  is  loaded  with 
stone  until  it  rests  firmly  on  the 
ground.  In  some  cases  the  stone 
is  merely  thrown  hi,  the  regular 
masonry  commencing  with  the 
top  of  the  caisson ;  which  is  sunk 
a  little  below  the  level  of  low 
water,  so  that  the  whole  of  the 
timber  is  always  covered,  and 
the  caisson  remains  as  part  of  the  structure.  In  others,  the  ma- 
sonry is  built  on  the  bottom  of  the  caisson,  and  when  the  work 
reaches  the  level  of  the  water  the  sides  of  the  caisson  are  removed. 
The  site  is  prepared  to  receive  the  caisson  by  dredging  and  depositing 
a  layer  of  concrete,  or  by  driving  piles,  or  a  combination  of  both. 


Fig.  14.    Building  on  Pile  Foundation. 


52  MASONRY  CONSTRUCTION 


The  inverted  caisson  is  also  a  strong  water-tight  box,  open  at  the 
bottom  and  closed  at  the  top,  upon  which  the  structure  is  built,  and 
which  sinks  as  the. masonry  is  added.  This  type  of  caisson  is  usual] v 
aided  in  sinking  by  excavation  made  in  the  interior.  The  processes 
employed  to  aid  the  sinking  of  the  inverted  caissons  are  called  the 
"vacuum"  and  the  "plenum." 

The  vacuum  process  consists  in  exhausting  the  air  from  the 
interior  of  the  caisson,  and  using  the  pressure  of  the  atmosphere  upon 
the  top  of  it  to  force  it  down.  Exhausting  the  air  allows  the  water  to 
flow  past  the  lower  edge  into  the  interior,  thus  loosening  the  soil. 

The  plenum  or  compressed-air  process  consists  in  pumping  air 
into  the  chamber  of  the  caisson,  which  by  its  pressure  excludes  the 
water.  An  air  lock  or  entrance  provided  with  suitable  doors  is  ar- 
ranged in  the  top  of  the  caisson,  by  which  workmen  can  enter  to 
loosen  up  the  soil  and  otherwise  aid  in  the  sinking  of  the  caisson 
vertically  by  removing  and  loosening  the  material  at  the  sides.  If 
the  loosened  material  is  of  a  suitable  character  it  is  removed  with  a 
sand  pump;  if  not,  hoisting  apparatus  is  provided  and,  being  loaded 
into  buckets  by  the  workmen,  it  is  hoisted  out  through  the  air  lock. 

Freezing  Process.  This  process  is  employed  in  sinking 
foundation-  pits  through  quicksand  and  soils  saturated  with  water. 
The  Poctsch-Sooysmith  process  is  to  sink  a  series  of  pipes  10  inches 
in  diameter  through  the  earth  to  the  rock;  these  are  sunk  in  a  circle 
around  the  proposed  shaft.  Inside  of  the  10-inch  pipes  8-inch  pipes 
closed  at  the  bottom  are  placed,  and  inside  of  these  are  placed  smaller 
pipes  open  at  the  bottom.  Each  set  of  the  small  pipes  is  connected 
in  a  series.  A  freezing  mixture  is  then  allowed  to  flow  downwards 
through  one  set  of  the  smaller  pipes  and  return  upwards  through  the 
other.  The  freezing  mixture  flows  from  a  tank  placed  at  a  suffic- 
ient height  to  cause  the  liquid  to  flow  with  the  desired  velocity  through 
the  pipes.  The  effect  of  this  process  is  to  freeze  the  earth  into  a  solid 

wall. 

DESIGNING   THE    FOUNDATION. 

Load  to  be  Supported.  The  first  step  is  to  ascertain  the  load 
to  be  supported  by  the  foundation.  This  load  consists  of  three  parts : 
(1)  The  structure  itself,  (2)  the  movable  loads  on  the  floors  and  the 
snow  on  the  roof,  and  (3)  the  part  of  the  load  that  may  be  transferred 
from  one  part  of  the  foundation  to  the  other  by  the  force  of  the  wind. 


MASONRY  CONSTRUCTION 


The  weight  of  the  building  is  easily  ascertained  by  calculating  the 
cubical  contents  of  all  the  various  materials  in  the  structure.  The  fol- 
lowing data  will  be  useful  in  determining  the  weight  of  the  structure. 

TABLE  8. 
Weight  of  Masonry. 


Kind  of  Masonry. 


Weight  in 
Ib.  per  cu.  ft. 


Brickwork,  pressed  brick,  thin  joints 


ordinary  quality 

soft  brick,  thick  joints 


Concrete 

Granite  or  limestone,  well  dressed  throughout 


rubble,  well  dressed  with  mortar .... 

roughly  dressed  with  mortar 

well  dressed,  dry 

roughly  dressed,  dry 


Mortar  dried 

Sandstone,  -fa  less  than  granite 


145 
125 
100 

130  to  160 
165 
155 
150 
140 
125 
100 


Ordinary  lathing  and  plastering  weighs  about  10  Ib.  per  sq.  ft. 
Floors  weigh  approximately: 

Dwellings 10  Ib.  per  sq.  ft. 

Public  buildings 25  Ib.  per  sq.  ft. 

Warehouses 40  to  50  Ib.  per  sq.  ft. 

Roofs  vary  according  to  the  kind  of  covering,  span,  etc. 
Shingle  roof  weighs  about  10  Ib.  per  sq.  ft. 

Slate  or  corrugated  iron 25  Ib  per  sq.  ft. 

The  movable  load  on  the  floor  depends  upon  the  nature  of  the 
building.  It  is  usually  taken  as  follows: 

Dwellings 10  Ib.  per  sq.  ft. 

Office  buildings 20  Ib.  per  sq.  ft. 

Churches,  theatres,  etc 100  Ib.  per  sq.  ft. 

Warehouses,  factories 100  to  400  Ib.  per  sq.  ft. 

The  weight  of  snow  on  the  roof  will  vary  from  0  in  a  warm 
climate  to  20  Ib.  in  the  latitude  of  Michigan.  The  pressure  of  the 
wind  is  usually  taken  at  50  Ib.  per  sq.  ft.  on  a  flat  surface  perpendicu- 
lar to  the  wind,  and  on  a  cylinder  at  about  40  Ibs.  per  sq.  ft.  over  the 
vertical  projection  of  the  cylinder. 


MASONRY  CONSTRUCTION 


Bearing  Power  of  Soils.  The  best  method  of  determining 
the  load  which  a  particular  soil  will  bear  is- by  direct  experiment  and 
examination — particularly  of  its  compactness  and  the  amount  of 
water  it  contains.  The  values  given  in  the  following  table  may  be 
considered  safe  for  good  examples  of  the  kind  of  soil  quoted. 

TABLE  9. 
Bearing  Power  of  Soils. 


Kind  of  soil. 

Bearing  power, 
tons  per  square  foot. 

Min.                Max. 

Rock  hard  

25 
5 
4 
2- 
1 
8 
4 
2 
0.5 

30 
10 
6  • 
4 
2 
10 
6 
4 
1 

"       soft  

Clay  on  thick  bed    always  dry  

"      "       "       "     moderately  dry  .  .  •  

"     soft  . 

Gravel  and  coarse  sand   well  cemented  •  • 

Sand   compact  and  well  cemented  •  • 

"      clean   dry     •         -  •  •    •     • 

Quicksand    alluvial  soil   etc    •    • 

Area  Required.  Having  determined  the  pressure  which  may 
safely  be  brought  upon  the  soil,  and  having  ascertained  the  weight 
of  each  part  of  the  structure,  the  area  required  for  the  foundation 
is  easily  determined  by  dividing  the  latter  by  the  former.  Then, 
having  found  the  area  required,  the  base  of  the  structure  must  be 
extended  by  footings  of  concrete,  masonry,  timber,  etc.,  so  as  to  (1) 
cover  that  area  and  (2)  distribute  the  pressure  uniformly  over  it. 

Bearing  Power  of  Piles.  Several  formulas  have  been  proposed 
and  are  in  use  for  determining  the  safe  working  loads  on  piles.  The 
three  in  general  use  are : 

Sander's  formula. 

,  .  Weight  of  hammer  in  Ib.  X  fall  in  inches. 

Safe  load  in  Ib.  =  •.,.      . 

8  X  Sinking  at  last  blow. 

Trautwine's  formula. 
Extreme  load  in  tons  of  2240  Ibs.  = 

Cube  root  of  fall  in  feet  X  Weight  of  hammer  in  Ib.  X  0.023 

Last  sinking  in  inches. 

Safe  load  to  be  taken  at  one-half  of   extreme  load  when  driven  in 
firm  soils,  and  at  one-fourth  when  driven  in  river  mud  or  marshy  soil. 


MASONRY  CONSTRUCTION 


55 


Engineering  News  formula  is  the  latest  and  is  considered  reliable. 

Safe  load  in  Ib.  = 

S  +  1 

in  which  w  =  weight  of  hammer  in  Ib.,  h  ==  its  fall  in  feet,  S  =  aver- 
age sinking  under  last  blows  in  inches. 

Example  of  Pile  Foundation.     As  an  example  of  the  method 
of  determining  the  number  of  piles  required  to  support  a  given  build- 
ing, the  side  walls  of  a  warehouse  are  selected,  a  vertical  section  of 
which  is   shown  in  Fig.    15.     The   walls   are   of 
brick,  and  the  weight  is  taken  at  110  pounds  per 
cubic  foot  of  masonry.  - 

The  piles  are  to  be  driven  in  two  rows, 
spaced  two  feet  between  centers,  and  it  has 
been  found  that  a  test  pile  20  feet  long  and  10 
inches  at  the  top  will  sink  one  inch  under  a 
1,200-pound  hammer  falling  20  feet  after  the 
pile  has  been  entirely  driven  into  the  soil. 
What  distance  should  the  piles  be  placed  center  to  center  length- 
wise of  the  wall  ? 

By  calculation  it  is  found  that  the  wall  contains  157J  cubic  feet 
of  masonry  per  running  foot,  and  hence  weighs  17,306  pounds.  The 
load  from  the  floors  which  comes  upon  the  wall  is: 

From  the  1st    floor.  .  .  1500  Ib. 


Fig.  15.    Stone 
Footing. 


3rd  " 

1380 

4th   "  

...  700 

5th   "  .  . 

790 

6th   "  

....     790 

roof  . 

.  240 

Total 0730  Ib. 

Hence  the  total  weight  of  the  wall  and  its  load  per  running  foot  is 
24,036  pounds. 

The  load  which  one  pile  will  support  is,  by  Sander's  rule 

1200  X  240 

=  36,000  pounds. 

o  X   1 

By  Trautwine's  rule,  using  a  factor  of  safety  of  2.5,  the  safe  load 
would  be 


56  MASONRY  GONSTRUCTK  )X 


X  1200  X  0.023 


=  15  tons  or  33,600  Ib. 


Z.O    X    (1      i      i) 

Then  one  pair  of  piles  would  support  72,000  or  07,200  pounds  ac- 
cording to  which  rule  we  take. 

Dividing  these  numbers  by  the  weight  of  one  foot  of  the  wall 
and  its  load,  it  is  found,  that,  by  Sander's  rule,  one  pair  of  piles  will 
support  3  feet  of  the  wall,  and,  by  Trautwine's  rule,  2.8  feet  of  wall; 
hence  the  pile  should  be  placed.  2  feet  9  inches  or  3  feet  between 
centers. 

DESIGNING  THE  FOOTING. 

The  term  footing  is  usually  understood  as  meaning  the  bottom 
course  or  courses  of  concrete,  timber,  iron,  or  masonry  employed 
to  increase  the  area  of  the  base  of  the  walls,  piers,  etc.  What- 
ever the  character  of  the  soil,  footings  should  extend  beyond 
the  fall  of  the  wall  (1)  to  add  to  the  stability  of  the  structure 
and  lessen  the  danger  of  its  being  thrown  out  of  plumb,  and 
(2)  to  distribute  the  weight  of  the  structure  over  a  larger 
area  and  thus  decrease  the  settlement  due  to  compression  of  the 
ground. 

Offsets  of  Footings.     The  area  of  the  foundation  having  been 

determined  and  its  center  having  been  located  with  reference  to  the 

axis  of  the  load,    the  next  step  is  to  deter- 

v  _  ^Bricks  _  H  mine    how   much     narrower  each     footing 

|        '   course  may  be  than  the  one  next  below  it. 
'     .  '   ' 


Tj — |       |      -|  The  proper  offset  for  each  course  will 


i*"    '',','    r- 1      depend     upon    the    vertical    pressure,     the 

Fig.  K5.   Bru-k  Footing.        transverse    strength    of    the   material,    and 

the  thickness   of  the  course.     Each  footing 

may  be  regarded  as  a  beam  fixed  at  one  end  and  uniformly 
loaded.  The  part  of  the  footing  course  that  projects  beyond 
the  one  above  it,  is  a  cantilever  beam  uniformly  loaded.  From 
the  formulas  for  such  beams,  the  safe  projection  may  be  cal- 
culated. 

Stone  Footings.  Table  10  gives  the  safe  offset  for  masonry 
footing  courses,  in  terms  of  the  thickness  of  the  course,  computed 
for  a  factor  of  safety  of  10. 


MASONBY  CONSTRUCTION 


57 


TABLE  10. 


Kind  of  stone. 

R* 
in  Ib.  per 
sq.  in. 

Offset  for  a  pressure 
in  tons  per  sq.  ft.  on 
the  bottom  of  the 
course  of 

0.5           1.0           2.0 

Bluestone 

ft* 

9  7OH 

3  6 

0  (\ 

1  8 

(Jranite  .  • 

1  800 

2  0 

9  1 

limestone 

i   2  7 

1  0 

1  3 

Sandstone 

1,200 

2.6 

1.8 

1.3 

Slate 

5,400 

5.0 

3.6 

2.5 

Best  hard 

l>rick 

1,500 

2.7 

1.9 

1.3 

Hard  brick 

800 

1  Q 

1  4 

0  8 

Concrete  1 

Portland  j 

2 

Sand         /•  10  davs  old  .  .  • 

lr)0 

0  8 

0  6 

0  4 

3 

Pebbles    ) 

Concrete  1 

Rosendale  ) 

2 

Sand            >  10  days  old  .... 

80 

0.6 

0.4 

0.3 

3 

Pebbles       \ 

*  Modulus  of  rupture. 

To  illustrate  the  method  of  using  the  preceding  table,  assume 
that  it  is  desired  to  determine  the  offset  for  a  limestone  footing  course 
when  the  pressure  on  the  bed  of  the  foundation  is  1  ton  per  square 
foot,  using  a  factor  of  safety  of  10.  On  the  table,  opposite  limestone, 
in  next  to  the  last  column,  we  find  the  quantity  1 .0.  This  shows  that 
under  the  conditions  stated,  the  offset  may  be  1.9  times  the  thickness 
of  the  course. 


Planff 
Fig  17.    Timber  Footing. 


Timber  Footing.     The  rise  of  the  transverse  timbers  (Fig.  17) 
may  be  calculated  by  the  following  formula: 

2  Xw  xy  X  s 
Breadth  in  inches  =  TV  s/   A 

D    /N  A. 


58 


MASONRY  CONSTRUCTION 


in  which  w  =  the  bearing  power  in  11).  per  sq.  ft.; 
p  ~  the  projection  of  the  beam  in  feet; 
s  =  the  distance  between  centers  of  beams  in  feet; 
D  =  the  assumed  depth  of  the  beam  in  inches; 
A  =  the  constant  for  strength  which  is  taken  for  Georgia 
pine  at  90,  oak  65,  Norway  pine  GO,  white  pine  or  spruce  55. 

Steel  I=Beam  Footings.     The  dimensions  of  the  I-beams,  Fig. 
18,  can  be  calculated  by  the  usual  formulas,  by  means  of  the  strain 


1 

I         I 

_ 

illLLLLL.  , 

1 

!                          1 

"-^ lO'O" ^— 


k  .......  -  ...........  I3'0"- 

Fig.  18.    Steel  I-IJeam  Footing. 


to  which  the  part  of  the  beam  in  cantilever  is  submitted*     The  safe 
load  per  running  foot  is  given  by  the  expression 


in  which  W  ==  load  in  pounds  per  running  foot; 

S  =  10,000  Ib.  per  sq.  in.,  extreme  fibre  strain  of  beams; 
m  =  distance  from  center  of  gravity  of  sections  to  top  or 

bottom; 
I  ==  moment  of  inertia  of  section,  neutral  axis  through 

center  of  gravity; 
'z  =  span  in  feet. 

A  ready  method  of  determining  the  size  of  the  beams  is  by  com- 
puting the  required  coefficient  of  strength,  and  finding  in  the  tables 
furnished  by  the  manufacturers  of  steel  beams  the  size  of  the  beam 


£  » .a& 

H   8   £« 

9115- 

SJJI 


c«    g    ce- 

g  S  sa 

«  w  || 

<3    Q    ta4 


^  O 


MASONRY  CONSTRUCTION 


59 


which  has  a  coefficient  equal  to,  or  next  above,  the  value  obtained  by 
the  formula.    C,  the  coefficient,  is  found  by  the  following  expression : 

C  =  4XwXp2Xs 

in  which  w  =  bearing  power  in  pounds  per  sq.  ft.; 
p  =  the  projection  of  the  beam  in  feet; 
s  —  the  spacing  of  the  beam,  center  to  center,  in  feet. 
Table  11  gives  the  safe  projection  of  steel  I-beams  spaced  on  I 
foot  centers  and  for  loads  varying  from  1  to  5  tons  per  sq.  ft. 

TABLE  11. 
Safe  Projection  of  I=Beam  Footings. 


b  (Tons  per  Square  Foot). 


Depth  of 
beam,  in. 

Weight 
per  foot, 
Ib. 

20 

'80 

20 

64 

15 

75 

15 

60 

15 

50 

15 

41 

12 

40 

12 

32 

10 

33 

10 

25.5 

9 

27 

9 

21 

8 

22 

8 

18 

7 

20 

7 

15.5 

6 

16 

6 

13 

5 

13 

5 

10 

4 

10 

4 

7.5 

1 

1« 

13* 

2 

254 

2y2 

3 

3% 

4 

4% 

5 

14.0 

12.5 

11.5 

10.0 

9.0 

9.0 

8.0 

7.5 

7.0 

6.5 

6.0 

12.5 

ll.C 

10.0 

8.5 

8.0 

8.0 

7.0 

6.5 

6.0 

6.0 

5.5 

11.5 

10.5 

9.5 

8.0 

7.5 

7.5 

6.5 

6.0 

6.0 

5.5 

5.0 

10.5 

9.5 

8.5 

7.5 

7.0 

6.5 

6.0 

5.5 

5.5 

5.0 

5.0 

9.5 

8.5 

8.0 

7.0 

6.5 

6.0 

5.5 

5.0 

5.0 

4.5 

4.5 

8.5 

8.0 

7.0 

6.0 

6.0 

5.5 

5.0 

4.5 

4.5 

4.0 

4.0 

8.0 

7.0 

6.5 

5.5 

5.5 

5.0 

4.5 

4.0 

4.0 

3.5 

3.5 

7.0 

6.5 

5.5 

5.0 

4.5 

4.5 

4.0 

4.0 

3.5 

3.5 

3.0 

6.5 

6.0 

5.5 

4.5 

4.5 

4.0 

4.0 

3.5 

3.5 

3.0 

3.0 

5.5 

5.0 

4.5 

4.0 

4.0 

3.5 

3.5 

3.0 

3.0 

2.5 

2.5 

5.5 

5.0 

4.5 

4.0 

4.0 

3.5 

3.5 

3.0 

3.0 

2.5 

2.5 

5.0 

4.5 

4.0 

3.5 

3.5 

3.0 

3.0 

2.5 

2.5 

2.5 

2.0 

5.0 

4.5 

4.0 

3.5 

3.5 

3.0 

3.0 

2.5 

2.5 

2.5 

2.0 

4.5 

4.0 

3.5 

3.0 

3.0 

3.0 

2.5 

2.5 

2.0 

2.0 

2.0 

4.5 

4.0 

3.5 

3.0 

3.0 

3.0 

2.5 

2.5 

2.0 

2.0 

2.0 

4.0 

3.5 

3.0 

2.5 

2.5 

2.5 

2.0 

2.0 

2.0 

2.0 

1.5 

3.5 

3.0 

3.0 

2.5 

2.5 

2.0 

2.0 

2.0 

1.5 

1.5 

1.5 

3.0 

3.0 

2.5 

2.5 

2.0 

2.0 

2.0 

1.5 

1.5 

1.5 

1.5 

3.0 

2.5 

2.5 

2.0 

2.0 

2.0 

1.5 

1.5 

1.5 

1.5 

1.5 

2.5 

2.5 

2.0 

2.0 

1.5 

1.5 

1.5 

1.5 

1.5 

2.5 

2.0 

2.0 

.1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

1.5 

1.5 

1.5 

1.5 

I 

1 

SAFE  WORKING  LOADS  FOR  HASONRY. 

BRICK  MASONRY  IN  WALLS  OR  PIERS. 

Tons  per  sq.  ft. 

Hard  brick  in  lime  mortar. 5  to    7 

Hard  brick  in  Rosendale  cement  1  to  3  ...  8  to  10 


60  MASONRY  CONSTRUCTION 

Tons  per  sq.  ft. 

Pressed  brick  in  lime  mortar 6  to    8 

Pressed  brick  in  Rosendale  cement 9  to  12 

Pressed  brick  in  Portland  cement 12  to  15 

Piers  exceeding  in  height  six  times  their  least  dimension  should 
be  increased  4  inches  in  size  for  each  additional  6  feet. 

According  to  the  New  York  building  laws,  brickwork  in  good 
lime  mortar  8  tons  per  sq.  ft.,  11J  tons  when  good  lime  and  cement 
mortar  is  used,  and  15  tons  when  good  cement  mortar  is  used. ' 

According  to  the  Boston  building  laws: 

Best  hard-burned  brick  (height  less  than  six  times  least  dimen- 
sion) with 

Lb.  per  sq.  ft. 

Mortar,  1  cement,  2  sand 30,000 

Mortar,  1  cement,  1  lime,  3  sand 24,000 

Mortar,  lime  . 16,000 

Best  hard-turned  brick  (height  six  to  twelve  times  least  dimen- 
sion) with 

Mortar,  1  cement,  2  sand. 26,000 

Mortar,  1  cement,  1  lime,  3  sand 20,000 

Mortar,  lime 14,000 

For  light  hard-burned  brick  use  f  the  above  amounts. 

STONE  MASONRY. 

Tons  per  sq.  ft. 

Rubble  walls,  irregular  stone 3 

Rubble  walls,  coursed,  soft  stone 2J 

Rubble  walls,  coursed,  hard  stone 5  to  16 

Dimension  stone  in  cement: 

Sandstone  and  limestone 10  to  20 

Granite 20  to  40 

Dressed  stone,  with  f-inch  dressed  joints,  in  cement: 

Granite 60 

Marble  or  limestone 40 

Sandstone 30 

Height  of  columns  not  to  exceed  eight  times  least  diameter. 
MORTARS. 

In  i  inch  joints  3  months  old:  Tons  per  sq.  ft. 

Portland  cement  1  to  4. .  40 


MASONRY  CONSTRUCTION  61 


Tons  per  sq.  ft. 

Rosendale  cement  1  to  3 13 

Lime  mortar 8  to  10 

Portland  1  to  2  in  |-inch  joints  for  bedding  iron  plates 70 

CONCRETE. 

Tons  per  sq.  ft. 

Portland  cement  1  to  S 8  to  20 

Rosendale  cement  1  to  6 , 5  to  10 

Lime,  best,  1  to  6 5 

HOLLOW  TILE. 

Pounds  per  sq.  ft. 

Hard  fire-clay  tiles 80 

Hard  ordinary  clay  tiles GO 

Porous  terra-cotta  tiles 40 

Terra-cotta  blocks,  unfilled 10,000 

Terra-cotta  blocks,  filled  solid  with  brick  or  cement 20,000 


CHICAGO  CLUB,  FORMERLY  THE  ART  INSTITUTE  OF  CHICAGO 

Burnham  &  Root,  Architects. 
Exterior  of  Brovvnstone.    Built  in  1888. 


MASONRY  CONSTRUCTION. 

v.' 

PART  II. 


CLASSIFICATION  OF  HASONRY. 

Masonry  is  classified  according  to  the  nature  of  the  material  used, 
as  " stone  masonry,"  "brick  masonry,"  "mixed  masonry,"  composed 
of  stones  and  bricks,  and  " concrete  masonry." 

Stone  masonry  is  classified  (1)  according  to  the  manner  in  which 
the  material  is  prepared,  as  "rubble  masonry,"  "squared  stone  ma- 
sonry," "ashlar  masonry,"  "broken  ashlar,"  and  the  combinations 
of  these  four  kinds;  and  (2)  according  to  the  manner  in  which  the 
work  is  executed,  as  "uncoursed  rubble,"  "coursed  rubble,"  "dry 
rubble,"  "regular-coursed  ashlar,"'  'broken  or  irregular-coursed 
ashlar,"  "ranged  work,"  "random  ranged,"  etc. 

DEFINITIONS  OF  THE  TERMS   USED  IN  MASONRY. 

Abutment:  (1)  That  portion  of  the  masonry  of  a  bridge  or 
dam  upon  which  the  ends  rest,  and  which  connects  the  superstruc- 
ture with  the  adjacent  banks.  '  (2)  A  structure  that  receives  the 
lateral  thrust  of  an  arch. 

Arris:  The  external  angle  or  edge  formed  by  the  meeting  of 
two  plane  or  curved  surfaces,  whether  walls  or  the  sides  of  a  stick 
or  stone. 

Backed  :     Built  on  the  rear  face. 

Backing :     The  rough  masonry  of  a  wall  faced  with  cut  stone. 

Batter :  The  slope  or  inclination  given  to  the  face  of  a  wall. 
It  is  expressed  by  dividing  the  height  by  the  horizontal  distance.  It 
is  described  by  stating  the  extent  of  the  deviation  from  the  vertical, 
as  one  in  twelve,  or  one  inch  to  the  foot. 

Bats :     Broken  bricks. 

Bearing  Blocks  or  Templets  :  Small  blocks  of  stone  built 
in  the  wall  to  support  the  ends  of  particular  beams. 


64  MASONRY  CONSTRUCTION 


Belt  Stones  or  Courses :  Horizontal  bands  or  zones  of  stone 
encircling  a  building  or  extending  through  a  wall. 

Blocking  Course :  A  course  of  stone  placed  on  the  top  of  a 
cornice,  crowning  the  walls. 

Bond:  The  disposing  of  the  blocks  of  stone  or  bricks  in  the 
walls  so  as  to  form  the  whole  into  a  firm  structure  by  a  judicious  over- 
,  lapping  of  each  other  so  as  to  break  joint. 

A  stone  or  brick  which  is  laid  with  its  length  across  the  wall,  or 
extends  through  the  facing  course  into  that  behind,  so  as  to  bind  the 
facing  to  the  backing,  is  called  a  "Loader"  or  "bond."  Bonds  are 
described  by  various  names,  as: 

Binders,  when  they  extend  only  a  part  of  the  distance  across 
the  wall. 

Through  Bonds,  when  they  extend  clear  across  from  face  to  back. 

Heart  Bonds,  when  two  headers  meet  in  the  middle  of  the  wall 
and  the  joint  between  them  is  covered  by  another  header. 

Perpend  Bond  signifies  that  a  header  extends  through  the  whole 
thickness  of  the  wall.  . 

Chain  Bond  is  the  building  into  the  masonry  of  an  iron  bar, 
chain,  or  heavy  timber. 

Cross  Bond,  in  which  the  joints  of  the  second  stretcher  course 
come  in  the  middle  of  the  first;  a  course  composed  of  headers  and 
stretchers  intervening. 

Block  and  Cross  Bond,  when  the  face  of  the  wall  is  put  up  in  cross 
bond  and  the  backing  in  block  bond. 

English  Bond  (brick  masonry)  consists  of  alternate  courses  of 
headers  and  stretchers. 

Flemish  Bond  (brick  masonry)  consists  of  alternate  headers  and 
stretchers  in  the  same  course. 

Blind  Bond  is  used  to  tie  the  front  course  to  the  wall  in  pressed 
brick  work  where  it  is  not  desirable  that  any  headers  should  be  seen 
in  the  face  work. 

To  form  this  bond  the  face  brick  is  trimmed  or  clipped  off  at 
both  ends,  so  that  it  will  admit  a  binder  to  set  in  transversely  from 
the  face  of  the  wall,  and  every  layer  of  these  binders  should  be  tied 
with  a  header  course  the  whole  length  of  the  wall.  The  binder  should 
be  put  in  every  fifth  course,  and  the  backing  should  be  done  in  a  most 
substantial  manner,  with  hard  brick  laid  in  close  joints,  for  the  reason 


MASONRY  CONSTRUCTION  65 


that  the  face  work  is  laid  in  a  fine  putty  mortar,  and  the  joints  con- 
sequently close  and  tight;  and  if  the  backing  is  not  the  same  the 
pressure  upon  the  wall  will  make  it  settle  and  draw  the  wall  inward. 
The  common  form  of  bond  in  brickwork  is  to  lay  three  or  five  courses 
as  stretchers,  then  a  header  course. 

Breast  Wall :  One  built  to  prevent  the  falling  of  a  vertical 
face  cut  into  the  natural  soil;  in  distinction  to  a  retaining  wall,  etc. 

Brick   Ashlar :     Walls  with  ashlar  facing  backed  with  bricks. 

Build  or  Rise  :  That  dimension  of  the  stone  which  is  per- 
pendicular to  the  quarry  bed. 

Buttress  :  A  vertical  projecting  piece  of  stone  or  brick  masonry 
built  in  front  of  a  wall  to  strengthen  it, 

Closers  are  pieces  of  brick  or  stone  inserted  in  alternate  courses 
of  brick  and  broken  ashlar  masonry  to  obtain  a  bond. 

Cleaning  Down  consists  in  washing  and  scrubbing  the  stone- 
work with  muriatic  acid  and  water.  Wire  brushes  are  generally 
used  for  marble  and  sometimes  for  sandstone.  Stiff  bristle  brushes 
are  ordinarily  used.  The  stones  should  be  scrubbed  until  all  mortar 
stains  and  dirt  are  entirely  removed. 

For  cleaning  old  stonework  the  sand  blast  operated  either  by 
steam  or  compressed  air  is  used.  Brick  masonry  is  cleaned  in  the 
same  manner  as  stone  masonry.  During  the  process  of  cleaning  all 
open  joints  under  window  sills  and  elsewhere  should  be  pointed. 

Coping  :  The  coping  of  a  wall  consists  of  large  and  heavy 
stones,  slightly  projecting  over  it  at  both  sides,  accurately  bedded  on 
the  wall,  and  jointed  to  each  other  with  cement  mortar.  Its  use  is 
to  shelter  the  mortar  in  the  interior  of  the  wall  from  the  weather,  and 
to  protect  by  its  weight  the  smaller  stones  below  it  from  being  knocked 
off  or  picked  out.  Coping  stones  should  be  so  shaped  that  water 
may  rapidly  run  off  from  them. 

For  coping  stones  the  objections  with  regard  to  excess  of  length 
do  not  apply;  this  excess  may,  on  the  contrary,  prove  favorable, 
because,  the  number  of  top  joints  being  thus  diminished,  the  mass 
beneath  the  coping  will  be  better  protected. 

Additional  stability  is  given  to  a  coping  by  so  connecting  the 
coping  stones  together  that  it  is  impossible  to  lift  one  of  them  without 
at  the  same  time  lifting  the  ends  of  the  two  next  it.  This  is  done 
either  by  means  of  iron  cramps  inserted  into  holes  in  the  stone  and 


MASONRY  CONSTRUCTK  )X 


fixed  there  with  lead,  or,  better  still,  by  means  of  dowels  of  wrought 
iron,  cast  iron,  copper,  or  hard  stone.  The  metal  dowels  are  inferior 
in  durability  to  those  of  hard  stone,  though  superior  in  strength. 
Copper  is  strong  and  durable,  but  expensive.  The  stone  dowels  are 
small  prismatic  or  cylindrical  blocks,  each  of  which  fits  into  a  pair 
of  opposite  holes  in  the  contiguous  ends  of  a  pair  of  coping  stones 
and  fixed  with  cement  mortar. 

The  under  edge  should  be  throated  or  dipped,  that  is,  grooved, 
so  that  the  drip  will  not  run  back  on  the  wall,  but  dror>  from  the  edge. 
Coping  is  divided  into  three  kinds. 

Parallel  coping,  level  on  top.  Feather-edged  coping,  bedded 
level  and  sloping  on  top.  SaddMxick  copnuj  lias  a  curved  or  doubly 
inclined  top. 

Corbell :  A  horizontal  projecting' piece,  or  course,  of  inasonrv 
which  assists  in  supporting  one  resting  upon  it  which  projects  still 
further. 

Cornice  :  The  ornamental  projection  at  the  eaves  of  a  building 
or  at  the  top  of  a  pier  or  any  other  structure. 

Counterfort:  Vertical  projections  of  stone  or  brick  masonry 
built  at  intervals  along  the  back  of  a  wall  to  strengthen  it,  and  gen- 
erally of  very  little  use. 

Course:  The  term  course  is  applied  to  each  horizontal  row  or 
layer  of  stones  or  bricks  in  a  wall;  some  of  the  courses  have  particular 
names,  as: 

Plinth  Course,  a  lower,  projecting,  square-faced  course;  also 
called  the  water  table. 

Blocking  Course,  laid  on  top  of  the  cornice. 

Bonding  Course,  one  in  which  the  stones  or  bricks  lie  with  their 
length  across  the  wall;  also  called  heading  course. 

Stretching  Course,  consisting  of  stretchers. 

Springing  Course,  the  course  from  which  an  arch  springs. 

String  Course,  a  projecting  course. 

Rowlock  Course,  bricks  set  on  edge. 

Cramps :  Bars  of  iron  having  the  ends  turned  at  right  angles 
to  the-  body  of  the  bar,  and  inserted  in  holes  and  trenches 
cut  in  the  upper  sides  of  adjacent  stones  to  hold  them  together 
(see  Coping). 


HOUSE  IN  WASHINGTON,  D.  C. 

Wood,  Donn  &  Deming,  Architects,  Washington,  D.  C. 

Doric  Colonial  Front. 


MASONRY  CONSTRUCTION  67 


Cutwater  or  Starling :  The  projecting  ends  of  a  bridge- 
pier,  etc.,  usually  so  shaped  as  to  allow  water,  ice,  etc.,  to  strike  them 
with  but  little  injury. 

Dowels :  Straight  bars  of  iron,  copper,  or  stone,  which  are 
placed  in  holes  cut  in  the  upper  bed  of  one  stone  and  in  the  lower  bed 
of  the  next  stone  above.  They  are  also  placed  horizontally  in  the 
adjacent  ends  of  coping  stones  (see  under  Coping).  Cramps  arfd 
dowels  are  fastened  in  place  by  pouring  melted  lead,  sulphur,  or 
cement  grout  around  them. 

Dry  Stone  Walls  may  be  of  any  of  the  classes  of  masonry 
previously  described,  with  the  single  exception  that  the  mortar  is 
omitted.  They  should  be  built  according  to  the  principles  laid  down 
for  the  class  to  which  they  belong. 

Face  :     The  front  surface  of  the  wall. 

Facing :  The  stone  which  forms  the  face  or  outside  of  the  wall 
exposed  to  view. 

Footing  :  The  projecting  courses  at  the  base  of  a  wall  for  the 
purpose  of  distributing  the  weight  over  an  increased  area,  and  thereby 
diminishing  the  liability  to  vertical  settlement  from  compression  of 
the  ground. 

Footings,  to  have  any  useful  effect,  must  be  securely  bonded 
into  the  body  of  the  work,  and  have  sufficient  strength  to  resist  the 
cross  strains  to  which  they  are  exposed.  The  beds  should  be  dressed 
true  and  parallel.  Too  much  care  cannot  be  bestowed  upon  the 
footing  courses  of  any  building,  as  upon  them  depends  much  of  the 
stability  of  the  work.  If  the  bottom  course  be  not  solidly  bedded, 
if  any  rents  or  vacuities  are  left  in  the  beds  of  the  masonry,  or  if  the 
materials  be  unsound  or  badly  put  together,  the  effects  of  such  care- 
lessness will  show  themselves  sooner  or  later,  and  always  at  a  period 
when  remedial  efforts  are  useless. 

Gauged  Work :  Bricks  cut  and  rubbed  to  the  exact  shape 
required. 

Grout  is  a  thin  or  fluid  mortar  made  in  the  proportion  of  1  of 
cement  to  1  or  2  of  sand.  It  is  used  to  fill  up  the  voids  in  walls  of 
rubble  masonry  and  brick.  Sometimes  the  interior  of  a  wall  is  built 
up  dry  and  grout  poured  in  to  fill  the  voids.  Unless  specifically 
instructed  to  permit  its  use,  grout  should  not  be  used  unless  in  the 
presence  of  the  inspector.  When  used  by  masons  without  instruc- 


68  MASONRY  CONSTRUCTION 

tions  it  is  usually  for  the  purpose  of  concealing  bad  work,     (irout  is 
used  for  solidifying  quicksand. 

Grouting  is  pouring  fluid  mcrtar  over  last  course  for  the  purpose 
of  filling  all  vacuities. 

Header.  Also  called  a  bond.  A  stone  or  brick  whose  greatest 
dimension  lies  perpendicular  to  the  face  of  the  wall,  and  used  for  the 
purpose  of  tying  the  face  to  the  backing  (see  Bond).  A  trick  of 
masons  is  to  use  "blind  headers,"  or  short  stones  that  look  like 
headers  on  the  face,  but  do  not  go  deeper  into  the  wall  than  the 
adjacent  stretchers.  When  a  course  has  been  put  on  top  of  these 
they  are  completely  covered  up,  and,  if  not  suspected,  the  fraud  will 
never  be  discovered  unless  the  weakness  of  the  wall  reveals  it. 

In  facing  brick  walls  with  pressed  brick  the  bricklayer  will  fre- 
quently cut  the  headers  for  the  purpose  of  economizing  the  more  expen- 
sive material ;  thus  great  watchfulness  is  necessary  to  secure  a  good  bond 
between  the  facing  and  common  brick.  "All  stone  foundation  walls 
21  inches  or  less  in  thickness  shall  have  at  least  one  header  extending 
through  the  wall  in  every  3  feet  in  height  from  the  bottom  of  the  wall,  and 
in  every  3  feet  in  length,  and  if  over  24  inches  in  thickness  shall  have  one 
header  for  every  6  superficial  feet  on  both  sides  of  the  wall,  and  fun- 
ning into  the  wall  at  least  2  feet.  All  headers  shall  be  at  least  ]  2  inches 
in  width  and  8  inches  in  thickness,  and  consist  of  good,  flat  stone. 

"  In  all  brick  walls  every  sixth  course  shall  be  a  heading  course, 
except  where  walls  are  faced  with  brick  in  running  bond,  in  which 
latter  case  every  sixth  course  shall  be  bonded  into  the  backing  by 
cutting  the  course  of  the  face  brick  and  putting  in  diagonal  headers 
behind  the  same,  or  by  splitting  the  face  brick  in  half  and  backing 
the  same  with  a  continuous  row  of  headers." 

Joints,  The  mortar  layers  between  the  stone  or  bricks  are 
called  the  joints.  The  horizontal  joints  are  called  "bed  joints;"  the 
end  joints  are  called  the  vertical  joints,  or  simply  the  "joints." 

Excessively  thick  joints  should  be  avoided.  In  good  brickwork 
they  should  be  about  J  to  J  inch  thick;  for  ashlar  masonry  and  pressed 
brickwork,  about  J  to  -^  inch  thick;  for  rubble  masonry  they  vary 
according  to  the  character  of  the  work. 

The  joints  of  both  stone  and  brick  masonry  are  finished  in 
different  ways,  with  the  object  of  presenting  a  neat  appearance  and 
of  throwing  the  rainwater  away  from  the  joint. 


MASONRY  CONSTRUCTION  69 


Flush  Joints.  In  these  the  mortar  is  pressed  flat  with  the  trowel 
and  the  surface  of  the  joint  is  flush  with  the  face  of  the  wall. 

Struck  Joints  are  formed  by  pressing  or  striking  back  with  the 
trowel  the  upper  portion  of  the  joint  while  the  mortar  is  moist,  so  as 
to  form, an  outward  sloping  surface  from  the  bottom  of  the  upper 
course  to  the  top  of  the  lower  course.  This  joint  is  also  designated 
by  the  name  "  weather  joint."  Masons  generally  form  this  joint  so 
that  it  slopes  inwards,  thus  leaving  the  upper  arris  of  the  lower  course 
bare  and  -exposed  to  the  action  of  the  weather.  The  reason  for  form- 
ing it  in  this  improper  manner  is  that  it  is  easier  to  perform. 

Key  Joints  are  formed  by  drawing  a  curved  iron  key  or  jointer 
along  the  center  of  the  flushed  joint,  pressing  it  hard,  so  that  the 
mortar  is  driven  in  beyond  the  face  of  the  wall;  a  groove  of  curved 
section  is  thus  formed,  having  its  surface  hardened  by  the  pressure. 

White  Skate  or  Groove  Joint  is  employed  in  front  brickwork.  It 
is  about  -j^ -inch  thick.  It  is  formed  with  a  jointer  having  the  width 
of  the  intended  joint.  It  is  guided  along  the  joint  by  a  straight  edge 
and  leaves  its  impress  upon  the  material. 

Joggle :  A  joint  piece  or  dowel  pin  let  into  adjacent  faces  of 
two  stones  to  hold,  them  in  position.  It  may  vary  in  form  and  ap- 
proach in  its  shape  either  the  dowel  or  clamp. 

Jamb  :     The  sides  of  an  opening  left  in  a  wall. 

Lintel  :  The  stone,  wood,  or  iron  beam  .used  to  cover  a  narrow 
opening  in  a  wall. 

One=Man  Stone  :  A  stone  of  such  size  as  to  be  readily  lifted 
by  one  man. 

Parapet  Wall  is  a  low  wall  running  along  the  edge  of  a  terrace 
or  roof  to  prevent  people  from  falling  over. 

Pointing  a  piece  of  masonry  consists  in  scraping  out  the  mortar 
in  which  the  stones  were  laid  from  the  face  of  the  joints  for  a  depth 
of  from  J  to  2  inches,  and  filling  the  groove  so  made  with  clear  Port- 
land-cement mortar,  or  with  mortar  made  of  1  part  of  cement  and 
1  part  of  sand. 

The  object  of  pointing  is  that  the  exposed  edges  of  the  joints 
are  always  deficient  in  density  and  hardness,  and  the  mortar  near  the 
surface  of  the  joint  is  specially  subject  to  dislodgment,  since  the  con- 
traction and  expansion  of  the  masonry  are  liable  either  to  separate 
the  stone  from  the  mortar  or  to  crack  the  mortar  in  the  joint,  thus 


70  MASONRY  CONSTRUCTION 


permitting  the  entrance  of  rainwater,  which  freezing  forces  the  mortar 
from  the  joints. 

The  pointing  mortar,  when  ready  for  use,  should  be  rather  inco- 
herent and  quite  deficient  in  plasticity. 

Before  applying  the  pointing,  the  joint  must  be  well  cleansed  by 
scraping  and  brushing  .out  the  loose  matter,  then  thoroughly  saturated 
with  water,  and  maintained  in  such  a  condition  of  dampness  that  the 
stones  will  neither  absorb  water  from  the  mortar  nor  impart  any  to  it. 
Walls  should  not  be  allowed  to  dry  too  rapidly  after  pointing. 

Pointing  should  not  be  prosecuted  either  during  free/ing  or 
excessively  hot  weather. 

The  pointing  mortar  is  applied  with  a  mason's  trowel,  and  the 
joint  well  calked  with  a  calking- iron  and  hammer.  In  the  very  best 
work  the  surface  of  the  mortar  is  rubbed  smooth  with  a  steel  polishing 
tool.  The  form  given  to  the  finish  joint  is  the  same  as  described 
under  joints. 

Pointing  with  colored  mortar  is  frequently  employed  to  improve 
the  appearance  of  the  work.  Various  colors  are  used,  as  white,  black, 
red,  brown,  etc.,  different  colored  pigments  being  added  to  the  mortar 
to  produce  the  required  color. 

Tuck  Pointing,  used  chiefly  for  brickwork,  consists  of  a  project- 
ing ridge  with  the  edges  neatly  pared  to  an  uniform  breadth  of  about 
i-inch.  White  mortar  is  usually  employed  for  this  class  of  pointing. 

Many  authorities  consider  that  pointing  is  not  advisable  for  new 
work,  as  the  joints  so  formed  are  not  as  enduring  as  those  which  are 
finished  at  the  time  the  masonry  is  built.  Pointing  is,  moreover, 
often  resorted  to  when  it  is  intended  to  give  the  work  a  superior 
appearance,  and  also  to  conceal  defects  in  inferior  work. 

Pallets,  Plugs  :  Wooden  bricks  inserted  in  walls  for  fastening 
trim,  etc. 

Plinth  :     A  projecting  base  to  a  wall;  also  called  "water  table." 

Pitched- Face  Masonry :  That  in  which  the  face  of  the  stone 
is  roughly  dressed  with  the  pitching  chisel  so  as  to  give  edges  that  are 
approximately  true. 

Quarry-Faced  or  Rock-Faced  Masonry :  That  in  which  the 
face  of  the  stone  is  left  untouched  as  it  comes  from  the  quarry. 

Quoin :  A  cornerstone.  A  quoin  is  a  header  for  one  face  and 
a  stretcher  for  the  other. 


MASONRY  CONSTRUCTION  71 


Rip=Rap.  Rip-rap  is  composed  of  rough  undressed  stone.as  it 
comes  from  the  quarry,  laid  dry  about  the  base  of  piers,  abutments, 
slopes  of  embankments,  etc.,  to  prevent  scour  and  wash.  When 
used  for  the  protection  of  piers  the  stones  are  dumped  in  promis- 
cuously, their  size  depending  upon  the  material  and  the  velocity  of 
the  current.  Stones  of  15  to  25  cubic  feet  are  frequently  employed. 
When  used  for  the  protection  of  banks  the  stones  are  laid  by  hand 
to  a  uniform  thickness. 

Rise :  That  dimension  of  a  stone  which  is  perpendicular  to  its 
quarry  bed  (see  Build). 

Retaining  Wall  or  Revetment  t     A  wall  built  to  retain  eartJ 
deposited  behind  it  (see  Breast  Wall). 

Reveal :  The  exposed  portion  of  the  sides  of  openings  in  walk 
in  front  of  the  recesses  for  doors,  window  frames,  etc. 

Slope=Wall  Masonry  :  A  slope  wall  is  a  thin  layer  of  masonry 
used  to  protect  the  slopes  of  embankments,  excavations,  canals,  river 
banks,  etc.,  from  rain,  waves,  weather,  etc. 

Slips  :     See  Wood  Bricks. 

Spall :     A  piece  of  stone  chipped  off  by  the  stroke  of  a  hammer. 

Sill ;  The  stone,  iron,  or  wood  on  which  the  window  or  doo* 
of  a  building  rests.  In  setting  stone  sills  the  mason  beds  the  ends 
only;  the  middle  is  pointed  up  after  the  building  is  enclosed.  They 
should  be  set  perfectly  level  lengthwise,  and  have  an  inclination  cross- 
wise, so  the  water  may  flow  from  the  frame. 

Stone  Paving  consists  of  roughly  squared  or  unsquared  blocks 
of  stone  used  for  paving  the  waterway  of  culverts,  etc.;  it  is  laid  both 
dry  and  in  mortar. 

Starling :     See  Cutwater. 

Stretcher ;  A  stone  or  brick  whose  greatest  dimension  lies 
parallel  to  the  face  of  the  wall. 

String  Course  :  A  horizontal  course  of  brick  or  stone  masonry 
projecting  a  little  beyond  the  face  of  the  wall.  Usually  introduced 
for  ornament. 

Two=Men  Stone :  Stone  of  such  size  as  to  be  conveniently 
lifted  by  two  men. 

Toothing :  Unfinished  brickwork  so  arranged  that  every  alter- 
nate brick  projects  half  its  length. 

Water-Table :     See  Plinth. 


72  MASONRY  CONSTRUCTION 

Wood  Bricks,  Pallets,  Plugs,  or  Slips  are  pieces  of  wood 
laid  in  a  wall  in  order  the  better  to  secure  any  woodwork  that  it  may 
be  necessary  to  fasten  to  it.  Great  injury  is  often  done  to  walls  by 
driving  wood  plugs  into  the  joints,  as  they  are  apt  to  shake  the  work. 
Hollow  porous  terra-cotta  bricks  are  frequently  used  instead  of  wood 
bricks,  etc. 

PREPARATION  OF  THE  MATERIALS. 
STONE   CUTTING. 

Dressing  the  Stones,  The  stonecutter  examines  the  rough 
blocks  as  they  come  from  the  quarry  in  order  to  determine  whether 
the  blocks  will  work  to  better  advantage  as  a  header,  a  stretcher,  or  a 
cornerstone.  Having  decided  for  which  purpose  the  stone  is  suited, 
he  prepares  to  dress  the  bottom  bed.  The  stone  is  placed  with  bottom 
bed  up,  all  the  rough  projections  are  removed  with  the  hammer  and 
pitching  tool,  and  approximately  straight  lines  are  pitched  off  around 
its  edges;  then  a  chisel  draft  is  cut  on  all  the  edges.  These  drafts 
are  brought  to  the  same  plane  as  nearly  as  practicable  by  the  use  of 
two  straight  edges  having  parallel  sides  and  equal  widths,  and  the 
enclosed  rough  portion  is  then  dressed  down  with  the  pitching  tool 
or  point  to  the  plane  of  the  drafts.  The  entire  bed  is  then  pointed 
down  to  a  surface  true  to  the  straight  edge  when  applied  in  any  direc- 
tion— crosswise,  lengthwise,  and  diagonally. 

Lines  are  then  marked  on  this  dressed  surface  parallel  and  per- 
pendicular to  the  face  of  the  stone,  enclosing  as  large  a  rectangle  as 
the  stone  will  admit  of  being  worked  to,  or  of  such  dimensions  as  may 
be  directed  by  the  plan. 

The  faces  and  sides  are  pitched  off  to  these  lines.  A  chisel  draft 
is  then  cut  along  all  four  edges  of  the  face,  and  the  face  either 
dressed  as  required,  or  left  rock  faced.  The  sides  are  then  pointed 
down  to  true  surfaces  at  right  angles  to  the  bed.  The  stone  is 
turned  over  bottom  bed  down,  and  the  top  bed  dressed  in  the  same 
manner  as  the  bottom.  It  is  important  that  the  top  bed  be  exactly 
parallel  to  the  bottom  bed  in  order  that  the  stone  may  be  of  uniform 
thickness. 

Stones  having  the  beds  inclined  to  each  other,  as  skewbacks,  or 
stones  having  the  sides  inclined  to  the  beds,  are  dressed  by  using  a 
bevelled  straight  edge  set  to  the  required  inclination. 


MASONRY  CONSTRUCTION  73 

Arch  stones  have  two  plane  surfaces  inclined  to  each  other;  these 
are  called  the  beds.  The  upper  surface  or  extrados  is  usually  left 
rough;  the  lower  surface  or  intrados  is  cut  to  the  curve  of  the  arch. 
This  surface  and  the  beds  are  cut  true  by  the  use  of  a  wooden  or 
metal  templet  which  is  made  according  to  the  drawings  furnished  by 
the  engineer  or  architect. 

TOOLS  USED  IN  STONE  CUTTING. 

The  Double=Face  Hammer  is  a  heavy  tool,  weighing  from  20 
to  30  pounds,  used  for  roughly  shaping  stones  as  they  come  from  the 
quarry  and  for  knocking  off  projections.  This  is  used  for  only  the 
roughest  work. 

The  Face  Hammer  has  one  blunt  and  one  cutting  end,  and  is 
used  for  the  same  purpose  as  the  double-face  hammer  where  less 
weight  is  required.  The  cutting  end  is  used  for  roughly  squaring 
stones  preparatory  to  the  use  of  the  finer  tools. 

The  Cavil  has  one  blunt  and  one  pyramidal  or  pointed  end, 
and  weighs  from  15  to  20  pounds.  It  is  used  in  quarries  for  roughly 
shaping  stone  for  transportation. 

The  Pick  somewhat  resembles  the  pick  used  in  digging,  and  is 
used  for  rough  dressing,  mostly  on  limestone  and  sandstone.  Its 
length  varies  from  15  to  24  inches,  the  thickness  at  the  eye  being 
about  2  inches. 

The  Axe  or  Pean  Hammer  has  two  opposite  cutting  edges. 
It  is  used  for  making  drafts  around  the  arris  or  edge  of  stones,  and  in 
reducing  faces,  and  sometimes  joints,  to  a  level.  Its  length  is  about 
10  inches  and  the  cutting  edge  about  4  inches.  It  is  used  after  the 
point  and  before  the  patent  hammer. 

The  Tooth  Axe  is  like  the  axe,  except  that  its  cutting  edges 
are  divided  into  teeth,  the  number  of  which  varies  with  the  kind  of 
work  required.  This  tool  is  not  used  in  cutting  granite  or  gneiss. 

The  Bush  Hammer  is  a  square  prism  of  steel,  whose  ends  are 
cut  into  a  number  of  pyramidal  points.  The  length  of  the  hammer 
is  from  4  to  8  inches  and  the  cutting  face  from  2  to  4  inches  square. 
The  points  vary  in  number  and  in  size  with  the  work  to  be  done. 
One  end  is  sometimes  made  with  a  cutting  edge  like  that-  of  the  axe. 

The  Crandall  is  a  malleable-iron  bar  about  2  feet  long  slightly 
flattened  at  one  end.  In  this  end  is  a  slot  3  inches  long  and  jj-inch 


74  MASONRY  CONSTRUCTION 

wide.  Through  this  slot  are  passed  ten  double-headed  points  of 
J-inch  square  steel  9  inches  long,  which  are  held  in  place  by  a  key. 

The  Patent  Hammer  is  a  double-headed  tool  so  formed  as  to 
hold  at  each  end  a  set  of  wide  thin  chisels.  The  tool  is  in  two  parts, 
which  are  held  together  by  the  bolts  which  hold  the  chisels.  Lateral 
motion  is  prevented  by  four  guards  on  one  of  the  pieces.  The  tool 
without  the  teeth  is  5J  X  2f  X  1^  inches.  The  teeth  are  2}  inches 
wide;  their  thickness  varies  from  Ty  to  ^  of  an  inch.  This  tool  is  used 
for  giving  a  finish  to  the  surface  of  stones. 

The  Hand  Hammer,  weighing  from  2  to  5  pounds,  is  used  in 
drilling  holes  and  in  pointing  and  chiselling  the  harder  rocks. 

The  Mallet  is  used  where  the  softer  limestones  and  sandstones 
are  cut. 

The  Pitching  Chisel  is  usually  of  IJ-inch  octagonal  steel, 
spread  on  the  cutting  edge  to  a  rectangle  of  J  X  2^  inches.  It  is  used 
to  make  a  well-defined  edge  to  the  face  of  a  stone,  a  line  being  marked 
on  the  joint  surface,  to  which  the  chisel  is  applied  and  the  portion  of 
the  stone  outside  of  the  line  broken  off  by  a  blow  with  the  hand  ham- 
mer on  the  head  of  the  chisel. 

The  Point  is  made  of  round  or  octagonal  steel  from  J  to  1  inch  in 
diameter.  It  is  made  about  12  inches  long,  with  one  end  brought  to 
a  point.  It  is  used  until  its  length  is  reduced  to  about  5  inches.  It 
is  employed  for  dressing  off  the  irregular  surface  of  stones,  either  for 
a  permanent  finish  or  preparatory  to  the  use  of  the  axe.  According 
to  the  hardness  of  the  stone,  either  the  hand  hammer  or  the  mallet 
is  used  with  it. 

The  Chisel  is  of  round  steel  of  J  to  f-inch  diameter  and  about 
10  inches  long,  with  one  end  brought  to  a  cutting  edge  from  J  inch 
to  2  inches  wide;  is  used  for  cutting  drafts  or  margins  on  the  face  of 
stones. 

The  Tooth  Chisel  is  the  same  as  the  chisel,  except  that  the 
cutting  edge  is  divided  into  teeth.  It  is  used  only  on  marbles  and 
sandstones. 

The  Splitting  Chisel  is  used  chiefly  on  the  softer  stratified 
stones,  and  sometimes  on  fine  architectural  carvings  in  granite. 

The  Plug,  a  truncated  wedge  of  steel,  and  the  feathers  of  half- 
round  malleable  iron,  are  used  for  splitting  unstratified  stone.  A 
row  of  holes  is  made  with  the  drill  on  the  line  on  which  the  fracture 


MASONRY  CONSTRUCTION  75 

is  to  be  made;  in  each  of  these  two  feathers  are  inserted,  and  the  plugs 
lightly  driven  in  between  them.  The  plugs  are  then  gradually  driven 
home  by  light  blows  of  the  hand  hammer  on  each  in  succession  until 
the  stone  splits. 

Machine  Tools.  In  all  large  stone  yards  machines  are  used 
to  prepare  the  stone.  There  is  a  great  variety  in  their  form,  but 
since  the  kind  of  dressing  never  takes  its  name  from  the  machine 
which  forms  it,. it  will  be  neither  necessary  nor  profitable  to  attempt 
a  description  of  individual  machines.  They  include  stone  saws, 
stone  cutters,  stone  grinders,  stone  p'olishers,  etc. 

DEFINITION  OF  TERMS  USED  IN  STONE   CUTTING. 

Axed  :     Dressed  to  a  plane  surface  with  an  axe. 

Boasted  or  Chiselled  :  Having  face  wrought  with  a  chisel  or 
narrow  tool. 

Broached:      Dressed  with  a  " punch"  after  being  droved. 

Bush  Hammered  :     Dressed  with  a  bush  hammer. 

Crandalled  :     Wrought  to  a  plane  with  a  crandall. 

Deadening  :  The  crushing  or  crumbling  of  a  soft  stone  under 
the  tools  while  being  dressed. 

Dressed  Work:  That  which  is'  wrought  on  the  face;  also 
applied  to  stones  having  the  joints  wrought  to  a  plane  surface,  but 
not  " squared." 

Drafted :  Having  a  narrow  chisel  draft  cut  around  the  face 
or  margin. 

Droved,  Stroked  :  Wrought  with  a  broad  chisel  or  hammer 
in  parallel  flutings  across  the  stone  from  end  to  end. 

Hammer  Dressed :     Worked  with  the  hammer. 

Herring  Bone  :     Dressed  in  angular  flutings. 

Nigged  or  Nidged  :  Picked  with  a  pointed  hammer  or  cavil 
to  the  desired  form. 

Patent  Hammered :     Dressed  with  a  patent  hammer. 

Picked :     Reduced  to  an  approximate  plane  with  a  pick. 

Pitched :  Dressed  to  the  neat  lines  or  edges  with  a  pitching 
chisel. 

Plain  :     Rubbed  smooth  to  remove  tool  marks. 

Pointed  :     Dressed  with  a  point  or  very  narrow  tool. 

Polished  :     Rubbed  down  to  a  reflecting  surface. 


76  MASONRY  CONSTRUCTION 

Prison  :     Having  surfaces  wrought  into  holes. 

Random  Tooled  or  Droved:  Cut  with  a  broad  tool  into 
irre'gular  flutings. 

Rock  Faced,  Quarry  Faced,  Rough :  Left  as  it  comes  from 
the  quarry.  It  may  be  drafted  or  pitched  to  reduce  projecting  points 
on  the  face  to  give  limits. 

Rubbed  :     See  Plain. 

Rustic,  Rusticated :  Having  the  faces  of  stones  projecting 
beyond  the  arrises,  which  are  bevelled  or  drafted.  The  face  may  be 
dressed  in  any  desired  manner. 

Scabble :  To  dress  off  the  angular  projections  of  stones  for 
rubble  masonry  with  a  stone  axe  or  hammer. 

Smooth :     See  Plain. 

Square  Droved :  Having  the  flutings  perpendicular  to  the 
lower  edge  of  the  stone. 

Striped  :     Wrought  into  parallel  grooves  with  a  point  or  punch. 

Stroked:     See  Droved. 

Tooled  :     Wrought  to  a  plane  with  an  inch  tool.     See  Droved. 

Toothed  :     Dressed  with  a  tooth  chisel. 

Vermiculated  Worm  Work:  Wrought  into  veins  by  cutting 
away  portions  of  the  face. 

METHODS  OF   FINISHING  THE   FACES  OF  CUT  STONE, 

In  architecture  there  are  a  great  many  ways  in  which  the  faces 
of  cut  stone  may  be  dressed,  but  the  following  are  those  that  will  be 
usually  met  in  engineering  work. 

Rough  Pointed.  WThen  it  is  necessary  to  remove  an  inch  or 
more  from  the  face  of  a  stone  it  is  done  by  the  pick  or  heavy  point 
until  the  projections  vary  from  -J-  to  1  inch.  The  stone  is  said  to  be 
rough  pointed.  In  dressing  limestone  and  granite  this  operation 
precedes  all  others. 

Fine  Pointed.  If  a  smoother  finish  is  deshed  rough  pointing 
is  followed  by  fine  pointing,  which  is  done  with  a  fine  point.  Fine 
pointing  is  used  only  where  the  finish  made  by  it  is  to  be  final,  and 
never  as  a  preparation  for  a  final  finish  by  another  tool. 

Crandalled.  This  is  only  a  speedy  method  of  pointing,  the 
effect  being  the  same  as  fine  pointing,  except  that  the  dots  on  the 
stone  are  more  regular.  The  variations  of  level  are  about  J  inch  and 


MASONRY  CONSTRUCTION 


77 


the  rows  are  made  parallel.     When  other  rows  at  right  angles  to  the 
first  are  introduced  the  stone  is  said  to  be  cross-crandalled. 

Axed  or  Pean  Hammered,  and  Patent  Hammered.  These 
two  vary  only  in  the  degree  of  smoothness  of  the  surface  which  is 
produced.  The  number  of  blades  in  a  patent  hammer  varies  from 
6  to  12  to  the  inch;  and  in  precise  specifications  the  number  of  cuts 
to  the  inch  must  be  stated,  such  as  6-cut,  8-cut,  10-cut,  12-cut.  The 


Pointed 


Fine  Pointed 


B  us/7-/!  0/77/77  erect 


Pafent-h  am  m  ere  d 


Cro>r>da//ed  Rock-face   with  Draff  Line 

Fig.  19.    Methods  of  Finishing  the  Faces  of  Cut  Stone. 

effect  of  axing  is  to  cover  the  surface  with  chisel  marks,  which  are 
made  parallel  as  far  as  practicable.     Axing  is  a  final  finish. 

Tooth  Axed.  The  tooth  axe  is  practically  a  number  of  points, 
and  it  leaves  the  surface  of  a  stone  in  the  same  condition  as  fine 
pointing.  It  is  usually,  however,  only  a  preparation  for  bush  ham- 
mering, and  the  work  is  then  done  without  regard  to  effect,  so  long 
as  the  surface  of  the  stone  is  sufficiently  levelled. 


78  MASONRY  CONSTRUCTION 


Bush  Hammered.  The  roughnesses  of  a  stone  are  pounded 
off  by  the  bush  hammer,  and  the  stone  is  then  said  to  be  "bushed." 
This  kind  of  finish  is  dangerous  on  sandstone,  as  experience  has 
shown  that  sandstone  thus  treated  is  very  apt  to  scale.  In  dressing 
limestone  which  is  to  have  a  bush  hammered  finish  the  usual  sequence 
of  operation  is  (1)  rough  pointing,  (2)  tooth  axing,  and  (3)  bush 
hammering. 

CLASSIFICATION  OF  THE  STONES. 

All  the  stones  used  in  building  are  divided  into  three  classes 
according  to  the  finish  of  the  surface,  viz.:  1.  Rough  stones  that 
are  used  as  they  come  from  the  quarry.  2.  Stones  roughly  squared 
and  dressed.  3.'  Stones  accurately  squared  and  finely  dressed. 

Unsquared  Stones.  This  class  covers  all  stones  which  are 
used  as  they  come  from  the  quarry  without  other  preparation  than 
the  removal  of  very  acute  angles  and  excessive  projections  from  the 
general  figure. 

Squared  Stones.  This  class  covers  all  stones  that  are  roughly 
squared  and  roughly  dressed  on  beds  and  joints.  The  dressing  is 
usually  done  with  the  face  hammer  or  axe,  or  in  soft  stones  with  the 
tooth  hammer.  In  gneiss,  hard  limestones,  etc.,  it  may  be  necessary 
to  use  the  point.  The  distinction  between  this  class  and  the  third 
lies  in  the  degree  of  closeness  of  the  joints.  Where  the  dressing  on 
the  joints  is  such  that  the  distance  between  the  general  planes  of  the 
surfaces  of  adjoining  stones  is  one-half  inch  or  more,  the  stones  prop- 
erly belong  to  this  class. 

Three  subdivisions  of  this  class  may  be  made,  depending  on  the 
character  of  the  face  of  the  stones. 

(a)  Quarry-faced  or  Rock-faced  stones  are  those  whose  faces  are 
left  untouched  as  they  come  from  the  quarry. 

(b)  Pitched-faced  stones  are  those  on  which  the  arris  is  clearly 
defined  by  a  line  beyond  which  the  rock  is  cut  away  by  the  pitching 
chisel,  so  as  to  give  edges  that  are  approximately  true. 

(c)  Drafted  stones  are  those  on  which  the  face  is  surrounded  by  a 
chisel  draft,  the  space  inside  the  draft  being  left  rough.     ( )rdinarily, 
however,  this  is  done  only  on  stones  in  which  the  cutting  of  the  joints 
is  such  as  to  exclude  them  from  this  class. 

In  ordering  stones  of  this  class  the  specifications  should  always 
state  the  width  of  the  bed  and  end  joints  which  are  expected,  and  also 


MASONRY  CONSTRUCTION  79 

how  far  the  surface  of  the  face  may  project  beyond  the  plane  of  the 
edge.  In  practice  the  projection  varies  between  1  inch  and  6  inches. 
It  should  also  be  specified  whether  or  not  the  faces  are  to  be  drafted. 
Cut  Stones.  This  class  covers  all  squared  stones  with  smoothly 
dressed  beds  and  joints.  As  a  rule,  all  the  edges  of  cut  stones  are 
drafted,  and  between  the  drafts  the  stone  is  smoothly  dressed.  The 
face,  however,  is  often  left  rough  where  construction  is  massive. 
The  stones  of  this  class  are  frequently  termed  " dimension"  stone  or 
"dimension"  work. 

ASHLAR  MASONRY. 

Ashlar  masonry  consists  of  blocks  of  stone  cut  to  regular  figures, 
generally  rectangular,  and  built  in  courses  of  uniform  height  or  rise, 
which  is  seldom  less  than  a  foot. 

Size  of  the  Stones.  In  order  that  the  stones  may  not  be 
liable  to  be  broken  across,  no  stone  of  a  soft  material,  such  as  the 
weaker  kinds  of  sandstone  and  granular  limestone,  should  have  a 
length  greater  than  3  times  its  depth  or  rise;  in  harder  materials  the 
length  may  be  4  to  5  times  the  depth.  The  breadth  in  soft  materials, 
may  range  from  1J  to  double  the  depth;  in  hard  materials  it  may  be 
3  times  the  depth. 

Laying  the  Stone.  The  bed  on  which  the  stone  is  to  be  laid 
should  be  thoroughly  cleansed  from  dust  and  well  moistened  with 
water.  A  thin  bed  of  mortar  should  then  be  spread  evenly  over  it, 
and  the  stone,  the  lower  bed  of  which  has  been  cleaned  and  moistened, 
raised  into  position,  and  lowered  first  upon  one  or  two  strips  of  wood 
laid  upon  the  mortar  bed;  then,  by  the  aid 'of  the  pinch  bar,  moved 
exactly  into  its  place,  truly  plumbed,  the  strips  of  wood  removed, 
and  the  stone  settled  in  its  place  and  levelled  by  striking  it  with  wooden 
mallets.  In  using  bars  and  rollers  in  handling  cut  stone,  the  mason 
must  be  careful  to  protect  the  stone  from  injury  by  a  piece  of  old 
bagging,  carpet,  etc. 

In  laying  "rock-faced"  work,  the  line  should  be  carried  above 
it,  and  care  must  be  taken  that  the  work  is  kept  plumb  with  the  cut 
margins  of  the  corners  and  angles. 

The  Thickness  of  Mortar  in  the  joints  of  well  executed 
ashlar  masonry  should  be  about  J-  of  an  inch,  but  it  is  usually  about  f . 

Amount  of  Mortar.  The  amount  of  mortar  required  for 
ashlar  masonry  varies  with  the  size  of  the  blocks,  and  also  with 


80  MASONRY  CONSTRUCTION 


the  closeness  of  the  dressing.  With  f  to  J-mch  joints  and  12  to 
20-inch  courses  will  be  about  2  cubic  feet  of  mortar  per  cubic  yard; 
with  larger  blocks  and  closer  joints,  there  will  be  about  1  cubic  foot 
of  mortar  per  yard  of  masonry.  Laid  in  1  to  2  mortar,  ordinary 
ashlar  will  require  J  to  J  of  a  barrel  of  cement  per  cubic  yard  of 
masonry. 

Bond  of  Ashlar  Masonry.  No  side  joint  in  any  course 
should  be  directly  above  a  side  joint  in  the  course  below;  but  the 
stones  should  overlap  or  break  joint  to  an  extent  of  from  once  to  once 
and  a  half  the  depth  or  rise  of  the  course.  This  is  called  the  bond  of 
the  masonry;  its  effect  is  to  cause  each  stone  to  be  supported  by  at 
least  two  stones  of  the  course  below,  and  assist  in  supporting  at  least 
two  stones  of  the  course  above;  and  its  objects  are  twofold:  first,  to 
distribute  the  pressure,  so  that  inequalities  of  load  on  the  upper  part 
of  the  structure,  or  of  resistance  at  the  foundation,  may  be  transmit- 
ted to  and  spread  over  an  increasing  area  of  bed  in  proceeding  down- 
wards or  upwards,  as  the  case  may  be;  and  second,  to  tie  the  structure 
together,  or  give  it  a  sort  of  tenacity,  both  lengthwise  and  from  face 
to  back,  by  means  of  the  friction  of  the  stones  where  they  overlap. 
The  strongest  bond  in  ashlar  masonry  is  that  in  which  each  course 
at  the  face  of  the  wall  contains  a  header  and  a  stretcher  alternately, 
the  outer  end  of  each  header  resting  on  the  middle  of  a  stretcher  of 
the  course  below,  so  that  rather  more  than  one-third  of  the  area  of 
the  face  consists  of  ends  of  headers.  This  proportion  may  be  devi- 
ated from  when  circumstances  require  it;  but  in  every  case  it  is  ad- 
visable that  the  ends  of  headers  should  not  form  less  than  one-fourth 
of  the  whole  area  of  the  face  of  the  wall. 

SQUARED=STONE  HASONRY. 

The  distinction  between  squared-stone  masonry  and  ashlar  lies 
in  the  character  of  the  dressing  and  the  closeness  of  the  joints.  In 
this  class  of  masonry  the  stones  are  roughly  squared  and  roughly 
dressed  on  beds  and  joints,  so  that  the  width  of  the  joints  is  half  an 
inch  or  more.  The  same  rules  apply  to  breaking  joint,  and  to  the 
proportions  which  the  lengths  and  breadths  of  the  stones  should  bear 
to  their  depths,  as  in  ashlar;  and  as  in  ashlar,  also,  at  least  one-fourth 
of  the  face  should  consist  of  headers,  whose  length  should  be  from 
three  to  five  times  the  depth  of  the  course. 


MASONRY  CONSTRUCTION  81 

Amount  of  Mortar.  The  amount  of  mortar  required  for 
squared-stone  masonry  varies  with  the  size  of  the  stones  and  with  the 
quality  of  the  masonry;  as  a  rough  average,  one-sixth  to  one-quarter 
of  the  mass  is  mortar.  When  laid  in  1  to  2  mortar,  from  J  to  f  of  a 
barrel  of  cement  will  be  required  per  cubic  yard  of  masonry. 

BROKEN  ASHLAR. 

Broken  ashlar  consists  of  cut  stones  of  unequal  depths,  laid  in 
the  wall  without  any  attempt  at  maintaining  courses  of  equal  rise, 
or  the  stones  in  the  same  course  of  equal  depth.  The  character  of 
the  dressing  and  closeness  of  the  joints  may  be  the  same  as  in  ashlar 
or  squared-stone  masonry,  depending  upon  the  quality  desired.  The 
same  rules  apply  to  breaking  joint,  and  to  the  proportions  which  the 
lengths  and  breadths  of  the  stones  should  bear  to  their  depths,  as  in 
ashlar;  and  as  in  ashlar,  also,  at  least  one-fourth  of  the  face  of  the 
wall  should  consist  of  headers. 

Amount  of  Mortar.  The  amount  of  mortar  required  when 
laid  in  1  to  2  mortar,  will  be  from  f  to  1  barrel  per  cubic  yard  of 
masonry,  depending  upon  the  closeness  of  the  joints. 

RUBBLE  MASONRY. 

Masonry  composed  of  unsquared  stones  is  called  rubble.  This 
class  of  masonry  covers  a  wide  range  of  construction,  from  the  com- 
monest kind  of  dry-stone  work  to  a  class  of  work  composed  of  large 
stones  laid  in  mortar.  It  comprises  two  classes:  (1)  uncoursed  rub- 
ble, in  which  irregular-shaped  stones  are  laid  without  any  attempt 
at  regular  courses,  and  (2)  coursed  rubble,  in  which  the  blocks  of 
unsquared  stones  are  levelled  off  at  specified  heights  to  an  approx- 
imately horizontal  surface.  Coursed  rubble  is  often  built  in  random 
courses;  that  is  to  say,  each  course  rests  on  a  plane  bed,  but  is  not 
necessarily  of  the  same  depth  or  at  the  same  level  throughout,  so 
that  the  beds  occasionally  rise  or  fall  by  steps.  Sometimes  it  is 
required  that  the  stone  shall  be  roughly  shaped  with  the  hammer. 

In  building  rubble  masonry  of  any  of  the  classes  above  men- 
tioned the  stone  should  be  prepared  by  knocking  off  all  the  weak 
angles  of  the  block.  It  should  be  cleansed  from  dust,  etc.,  and 
moistened  before  being  placed  on  its  bed.  Each  stone  should  be 
firmly  imbedded  in  the  mortar.  Care  should  be  taken  not  only  that 


82  MASONRY  CONSTRUCTION 


each  stone  shall  rest  on  its  natural  bed,  but  that  the  sides  parallel  to 
that  natural  bed  shall  be  the  largest,  so  that  the  stone  may  lie  flat, 
and  not  be  set  on  edge  or  on  end.  However  small  and  irregular  the 
stones,  care  should  be  taken  to  break  joints.  Side  joints  should  not 
form  an  angle  with  the  bed  joint  sharper  than  60°.  The  hollows  or 
interstices  between  the  larger  stones  must  be  filled  with  smaller  stones 
and  carefully  bedded  in  mortar. 

One-fourth  part  at  least  of  the  face  of  the  wall  should  consist  of 
bond  stones  extending  into  the  wall  a  length  of  at  least  3  to  5  times 
their  depth,  as  in  ashlar. 

Amount  of  Mortar,  If  rubble  masonry  is  composed  of  small 
and  irregular  stones,  about  .-J  of  the  mass  will  consist  of  mortar;  if 
the  stones  are  larger  and  more  regular  J  to  J  will  be  mortar.  Laid 
in  1  to  2  mortar,  ordinary  rubble  requires  from  i  to  1  barrel  of  cement 
per  cubic  yard  of  masonry. 

ASHLAR  BACKED  WITH  RUBBLE. 

In  this  class  of  masonry  the  stones  of  the  ashlar  face  should  have 
their  beds  and  joints  accurately  squared  and  dressed  with  the  hammer 
or  the  points,  according  to  the  quality  desired,  for  a  breadth  of  from 
once  to  twice  (or  on  an  average,  once  and  a  half),  the  depth  or  rise 
of  the  course,  inwards  from  the  face;  but  the  backs  of  these  stones 
may  be  rough.  The  proportion  and  length  of  the  headers  should  be 
the  same  as  in  ashlar,  and  the  "tails"  of  these  headers,  or  parts  which 
extend  into  the  rubble  backing,  may  be  left  rough  at  the  back  and 
sides;  but  their  upper  and  lower  beds  should  be  hammer  dressed  to 
the  general  plane  of  the  beds  of  the  course.  These  tails  may  taper 
slightly  in  breadth,  but  should  not  taper  in  depth. 

The  rubble  backing,  built  in  the  manner  described  under  Rubble 
Masonry,  should  be  carried  up  at  the  same  time  with  the  face  work, 
and  in  courses  of  the  same  rise,  the  bed  of  each  course  being  carefully 
formed  to  the  same  plane  with  that  of  the  facing. 

GENERAL  RULES  FOR  LAYING  ALL  CLASSES  OF 
STONE  MASONRY. 

1.  Build  the  masonry,  as  far  as  possible,  in  a  series  of  courses, 
perpendicular,  or  as  nearly  so  as  possible,  to  the  direction  of  the  pres- 
sure which  they  have  to  bear,  and  by  breaking  joints  avoid  all  long 
continuous  joints  parallel  to  that  pressure. 


AS(  )\  \\ V  ( X  INSTRUCTION 


83 


2.  Use  the  largest  stones  for  the  foundation  course. 

3.  Lay  all  stones  which  consist  of  layers  in  such  a  manner  that 
the  principal  pressure  which  they  have  to  bear  shall  act  in  a  direction 
perpendicular,  or  as  nearly  so  as  possible,  to  the  direction  of  the 
layers.     This  is  called  laying  the  stone  on  its  natural  bed,  and  is  of 
primary  importance  for  strength  and  durability. 

4.  Moisten  the  surface  of  dry  and  porous  stones  before  bedding 
them,  in  order  that  the  mortar  may  not  be  dried  too  fast  and  reduced 


Regular  Coursed  Ashlar. 


Random  Coursed  Ashlar. 


Rubble,  Undressed,  Laid  at  Random. 
Fig.  20. 


Random  Rubble  with  Hammer- Dressed  Joints  and 
no  Spalls  on  Face. 

Types  of  Masonry. 


to  powder  by  the  stone  absorbing  its  moisture. 

5.  Fill  every  part  of  every  joint  and  all  spaces  between  the 
stones  wTith  mortar,  taking  care  at  the  same  time  that  such  spaces 
shall  be  as  small  as  possible. 

6.  The  rougher  the  stones,  the  oetter  the  mortar  should  be. 
The  principal  object  of  the  mortar  is  to  equalize  the  pressure;  and 
the  more  nearly  the  stones  are  dressed  to  closely  fitting  surfaces,  the 
less  important  is  the  mortar.     Not  infrequently  this  rule  is  exactly 
reversed;  i.e.,  the  finer  the  dressing  the  better  the  quality  of  the 
mortar  used. 


84  MASONRY  CONSTRUCTION 

All  projecting  courses,  siich  as  sills,  lintels,  etc.,  should  be  covered 
with  boards,  bagging,  etc.,  as  the  work  progresses,  to  protect  them 
from  injury  and  mortar  stains. 

When  setting  cut  stone  a  pailful  of  clean  water  should  be  kept 
at  hand,  and  when  any  fresh  mortar  comes  in  contact  with  the  face 
of  the  work  it  should  be  immediately  washed  off. 

GENERAL  RULES  FOR  BUILDING  BRICK  MASONRY. 

1.  Reject  all  misshapen  and  unsound  bricks. 

2.  Cleanse  the  surface  of  each   brick,  and  wet  it  thoroughly 
before  laying  it,  in  order  that  it  may  not  absorb  the  moisture  of  the 
mortar  too  quickly. 

3.  Place  the  beds  of  the  courses  perpendicular,  or  as  nearly 
perpendicular  as  possible,  to  the  direction  of  the  pressure  which  they 
have  to  bear;  and  make  the  bricks  in  each  course  break  joint  with 
those  of  the  courses  above  and  below  by  overlapping  to  the  extent  of 
from  one-quarter  to  one-half  of  the  length  of  a  brick.     (For  the  style 
of  bond  used  in  brick  masonry,  see  under  Bond  in  list  of  definitions.) 

4.  Fill  every  joint  thoroughly  with  mortar. 

Brick  should  not  be  merely  laid,  but  every  one  should  be  rubbed 
and  pressed  down  in  such  a  manner  as  to  force  the  mortar  into  the 
pores  of  the  bricks  and  produce  the  maximum  adhesion ;  with  quick- 
setting  cement,  this  is  still  more  important  than  with  lime  mortar. 
For  the  best  work  it  is  specified  that  the  brick  shall  be  laid  with  a 
"shove  joint,"  that  .is,  that  the  brick  shall  first  be  laid  so  as  to  project 
over  the  one  below,  and  be  pressed  into  the  mortar,  and  then  be 
shoved  into  its  final  position. 

Bricks  should  be  laid  in  full  beds  of  mortar,  filling  end  and  side 
joints  in  one  operation.  This  operation  is  simple  and  easy  with 
skilful  masons — if  they  will  do  it — -but  it  requires  persistence  to  get 
it  accomplished.  Masons  have  a  habit  of  laying  brick  in  a  bed  of 
rnortar,  leaving  the  vertical  joints  to  take  care  of  themselves,  throwing 
a  little  mortar  over  the  top  beds  and  giving  a  sweep  with  the  trowel 
which  more  or  less  disguises  the  open  joint  below.  They  also  have 
a  way  after  mortar  has  been  sufficiently  applied  to  the  top  bed  of 
brick  to  draw  the  point  of  their  trowel  through  it,  making  an  open 
channel  with  only  a  sharp  ridge  of  mortar  on  each  side  (and  generally 
throwing  some  of  it  overboard),  so  that  if  the  succeeding  brick  is 


MASONRY  CONSTRUCTION  85 


taken  up  it  will  show  a  clear  hollow,  free  from  mortar  through  the 
bed.  This  enables  them  to  bed  the  next  brick  with  more  facility 
and  avoid  pressure  upon  it  to  obtain  the  requisite  thickness  of  joint. 


JL-UJLLIJLJL 


J I 


C 


rpnpriri      ~j_i 


JLL 


a 

Common  Bond.  English  Bond.  Flemish  Bond. 

Fig.  21.    Bond  Used  in  Brick  Masonry. 

With  ordinary  interior  work  a  common  practice  is  to  lay  brick 
with  J  and  j-inch  mortar  joints;  an  inspector  whose  duty  is  to  keep 
joints  down  to  J  or  f  inch  will  not  have  an  enviable  task. 

Neglect  in  wetting  the  brick  before  use  is  the  cause  of  most  of 
the  failures  of  brickwork.  Bricks  have  a  great  avidity  for  water,  and 
if  the  mortar  is  stiff  and  the  bricks  dry,  they  will  absorb  the  water 
so  rapidly  that  the  mortar  will  not  set  properly,  and  will  crumble  in 
the  fingers  when  dry.  Mortar  is  sometimes  made  so  thin  that  the 
brick  will  not  absorb  all  the  water.  This  practice  is  objectionable; 
it  interferes  with  the  setting  of  the  mortar,  and  particularly  with  the 
adhesion  of  the  mortar  to  the  brick.  Watery  mortar  also  contracts 
excessively  in  drying  (if  it  ever  does  dry),  which  causes  undue  settle- 
ment and,  possibly,  cracks  or  distortion. 

The  bricks  should  not  be  wetted  to  the  point  of  saturation,  or 
they  will  be  incapable  of  absorbing  any  of  the  moisture  from  the 
mortar,  and  the  adhesion  between  the  brick  and  mortar  will  be  weak. 

The  common  method  of  wetting  brick  by  throwing  water  from 
buckets  or  spraying  with  a  hose  over  a  large  pile  is  deceptive,  the 
water  reaches  a  few  brick  on  one  or  more  sides  and  escapes  many. 
Immersion  of  the  brick  for  from  3  to  8  minutes,  depending  upon  its 
quality,  is  the  only  sure  method  to  avert  the  evil  consequences  of 
using  dry  or  partially  wetted  brick. 

Strict  attention  must  be  paid  to  have  the  starting  course  level, 
for  the  brick  being  of  equal  thickness  throughout,  the  slightest 
irregularity  or  incorrectness  in  it  will  be  carried  into  the  superposed 
courses,  and  can  only  be  rectified  by  using  a  greater  or  less  quantity 
of  mortar  in  one  part  or  another,  a  course  which  is  injurious  to  the 
work. 


MASONRY  CONSTRUCTION 


A  common  but  improper  method  of  building  thick  brick  walls 
is  to  lay  up  the  outer  stretcher  courses  between  the  header  courses, 
and  then  to  throw  mortar  into,  the  trough  thus  formed,  making  it 
semi-fluid  by  the  addition  of  a  large  dose  of  water,  then  throwing  in 
the  brick  (bats,  sand,  and  rubbish  are  often  substituted  for  bricks), 
allowing  them  to  find  their  own  bearing;  when  the  trough  is  filled  it 
is  plastered  over  with  stiff  mortar  and  the  header  course  laid  and  the 
operation  repeated  This  practice  may  have  some  advantage  in 
celerity  in  executing  work,  but  none  in  strength  or  security. 

Amount  of  Mortar.  The  thickness  of  the  mortar  joints 
should  be  about  J  to  f  of  an  inch.  Thicker  joints  are  very  common, 
but  should  be  avoided.  If  the  bricks  are  even  fairly  good  the  mortar 
is  the  weaker  part  of  the  wall;  hence  the  less  mortar  the  better. 
Besides,  a  thin  layer  of  mortar  is  stronger  under  compression  than  a 
thick  one.  The  joints  should  be  as  thin  as  is  consistent  with  their 
insuring  a  uniform  bearing  and  allowing  rapid  work  in  spreading  the 
mortar.  The  joints  of  outside  walls  should  be  thin  in  order  to  de- 
crease the  disintegration  by  weathering.  The  joints  of  inside  walls 
are  usually  made  from  f  to  J-inch  thick. 

The  proportion  of  mortar  to  brick  will  vary  with  the  size  of  the 
brick  and  with  the  thickness  of  the  joint.  With  the  standard  brick 
(8J  X  4  X  2J  inches),  the  amount  of  mortar  required  will  be  as 
follows : 

Thickness  of  Joints.  Mortar  required. 

Per  Cubic  Yard.          Per  1,000  Brick. 
Cubic  Yards.  Cubic  Yards. 

}  to  J  inch 0.30  to  0.40  0.80  to  0.90 

1  "  I    "     0.20  "  0.30  0.40  "  0.60 

fc  "        "       0.10  "  0.15  0.15  "  0.20 

Face  or  Pressed  Brick  Work.  This  term  is  applied  to  the 
facing  of  walls  with  better  bricks  and  thinner  joints  than  the  backing. 
The  bricks  are  pressed,  of  various  colors,  and  are  laid  in  colored 
mortar.  The  bricks  are  laid  in  close  joints,  usually  g-inch  thick,  and 
set  with  an  imperceptible  batter  in  themselves,  which  may  not  be 
seen  when  looking  at  the  work  direct,  but  which  makes  the  joint  a 
prominent  feature  and  gives  the  work  a  good  appearance.  The 
brick  of  each  course  must  be  gauged  with  care  and  exactness,  so 
that  the  joints  may  appear  all  alike.  The  bond  used  for  the  face  of 


MASONRY  CONSTRUCTION  87 


the  wall  is  called  the  "running  bond/'  the  bricks  are  clipped  on  the 
back,  and  a  binder  placed  transversely  therein  to  bond  the  facing 
to  the  backing.  The  joints  in  the  backing  being  thicker  than  those 
of  the  face  work,  it  is  only  in  every  six  or  seven  courses  that  they  come 
to  the  same  level,  so  as  to  permit  headers  being  put  in.  This  class 
of  work  requires  careful  watching  to  see  that  the  binders  or  headers 
are  put  in ;  it  frequently  happens  that  the  face  work  is  laid  up  without 
having  any  bond  with  the  backing. 

In  white-joint  work  the  mortar  is  composed  of  white  sand  and 
fine  lime  putty.  The  mason  when  using  this  mortar  spreads  it  care- 
fully on  the  bed  of  the  brick  which  is  to  be  laid  in  such  a  way  that 
when  the  brick  is  set  the  mortar  will  protrude  about  an  inch  from  the 
face  of  the  wall.  When  there  are  a  number  laid,  and  before  the 
mortar  becomes  too  hard,  the  mortar  that  protrudes  is  cut  off  flush 
with  the  wall,  the  joint  struck  downwards,  and  the  upper  and  lower 
edges  cut  with  a  knife  guided  by  a  small  straight  edge.  When  the 
front  is  built,  the  whole  is  cleaned  down  with  a  solution  of  muriatic 
acid  and  water,  not  too  strong,  and  sometimes  oiled  with  linseed  oil 
cut  with  turpentine,  and  applied  with  a  flat  brush.  After  the  front 
is  thoroughly  cleaned  with  the  muriatic  acid  solution,  it  should  be 
washed  with  clean  water  to  remove  all  remains  of  the  acid. 

When  colored  mortars  are  required,  the  lime  and  sand  should 
be  mixed  at  least  10  days  before  the  colored  pigments  are  added  to 
it,  and  they  should  be  well  soaked  in  water  before  being  added  to 
the  mortar. 

BRICK  MASONRY  IMPERVIOUS  TO  WATER. 

It  sometimes  becomes  necessary  to  prevent  the  percolation  of 
water  through  brick  walls.  A  cheap  and  effective  process  has  not  yet 
been  discovered,  and  many  expensive  trials  have  proved  failures. 
Laying  the  bricks  in  asphaltic  mortar  and  coating  the  walls  with 
asphalt  or  coal  tar  are  successful.  "  Sylvester's  Process  for  Repelling 
Moisture  from  External  Walls,"  has  proved  entirely  successful.  The 
process  consists  in  using  two  washes  for  covering  the  surface  of  the 
walls,  one  composed  of  Castile  soap  and  water,  and  one  of  alum  and 
water.  These  solutions  are  applied  alternately  until  the  walls  are 
made  impervious  to  water. 


88  MASONRY  CONSTRUCTION 


EFFLORESCENCE. 

Masonry,  particularly  in  moist  climates  or  damp  places,  is  fre- 
quently disfigured  by  the  formation  of  a  white  efflorescence  on  the 
surface.  This  deposit  generally  originates  with  the  mortar.  The 
water  which  is  absorbed  by  the  mortar  dissolves  the  salts  of  soda, 
potash,  magnesia,  etc.,  contained  in  the  lime  or  cement,  and  on 
evaporating  deposits  these  salts  as  a  white  efflorescence  on  the  surface. 
With  lime  mortar  the  deposit  is  frequently  very  heavy,  and,  usually, 
it  is  heavier  with  Rosendale  than  with  Portland  cement.  The  efflor- 
escence sometimes  originates  in  the  brick,  particularly  if  the  brick 
was  burned  with  sulphurous  coal  or  was  made  from  clay  containing 
iron  pyrites;  and  when  the  brick  gets  wet  the  water  dissolves  the 
sulphates  of  lime  and  magnesia,  and  on  evaporating  leaves  the 
crystals  of  these  salts  on  the  surface.  The  crystallization  of  these 
salts  within  the  pores  of  the  mortar  and  of  the  brick  or  stone  causes 
disintegration,  and  acts  in  many  respects  like  frost. 

The  efflorescence  may  be  entirely  prevented  by  applying  "  Syl- 
vester's" washes,  composed  of  the  same  ingredients  and  applied  in 
the  same  manner  as  for  rendering  masonry  impervious  to  moisture. 
If  can  be  much  diminished  by  using  impervious  mortar  for  the  face 
of  the  joints. 

REPAIR  OF  flASONRY. 

In  effecting  repairs  in  masonry,  when  new  work  is  to  be  con- 
nected with  old,  the  mortar  of  the  old  must  be  thoroughly  cleaned 
off  along  the  surface  where  the  junction  is  to  be  made  and  the  surface 
thoroughly  wet.  The  bond  and  other  arrangements  will  depend 
upon  the  circumstances  of  the  case.  The  surfaces  connected  should 
be  fitted  as  accurately  as  practicable,  so  that  by  using  but  little  mortar 
no  disunion  may  take  place  from  settling. 

As  a  rule,  it  is  better  that  new  work  should  butt  against  the  old, 
either  with  a  straight  joint  visible  on  the  face,  or  let  into  a  chase, 
sometimes  called  a  "slip-joint,"  so  that  the  straight  joint  may  not 
show;  but  if  it  is  necessary  to  bond  them  together  the  new  work 
should  be  built  in  a  quick-setting  cement  mortar  and  each  part  of  it 
allowed  to  set  before  being  loaded. 

In  pointing  old  masonry  all  the  decayed  mortar  must  be  com- 
pletely raked  out  with  a  hooked  iron  point  and  the  surfaces  well 
wetted  before  the  fresh  mortar  is  applied. 


MASONRY  CONSTRUCTION  89 


flASONRY  STRUCTURES. 

The  component  parts  of  masonry  structures  may  be  divided 
into  several  classes  according  to  the  efforts  they  sustain,  their  forms 
and  dimensions  depending  on  these  efforts. 

1.  Those  which  sustain  only  their  own  weight,  and  are  not 
liable  to  any  cross  strain  upon  the  blocks  of  which  they  are  composed, 
as  the  walls  of  enclosures. 

2.  Those  which,  besides  their  own  weight,  sustain  a  vertical 
pressure  arising  from  a  weight  borne  by  them,  as  the  walls  of  edifices, 
columns,  the  piers  of  arches,  bridges,  etc. 

3..  Those  which  sustain  lateral  pressures  and  cross  strains, 
arising  from  the  action  of  earth,  water,  frames,  arches,  etc. 

4.  Those  which  sustain  a  vertical  upward  or  downward  pres- 
sure, and  a  cross  strain,  as  lintels,  etc. 

5.  Those  which  transfer  the  pressure  they  directly  receive  to 
lateral  points  of  support,  as  arches. 

WALLS. 

Walls  are  constructions  of  stone,  brick,  or  other  materials,  and 
serve  to  retain  earth  or  water,  or  in  buildings  to  support  the  roof  and 
floors  and  to  keep  out  the  weather.  The  following  points  should  be 
attended  to  in  the  construction  of  walls: 

The  whole  of  the  walling  of  a  building  should  be  carried  up 
simultaneously;  no  part  should  be  allowed  to  rise  more  than  about 
3  feet  above  the  rest;  otherwise  the  portion  first  built  will  settle  down 
to  its  bearings  before  the  other  is  attached  to  it,  and  then  the  settle- 
ment which  takes  place  in  the  newer  portion  will  cause  a  rupture, 
and  cracks  will  appear  in  the  structure.  If  it  should  be  necessary 
to  carry  up  one  part  of  a  wall  before  the  other,  the  end  of  that  portion 
first  built  should  be  racked  back,  that  is,  left  in  steps,  each  course  pro- 
jecting farther  than  the  one  above  it. 

Work  should  not  be  hurried  along  unless  done  in  cement  mortar, 
but  given  time  to  settle  to  its  bearings. 

Thickness  of  Walls.  The  thickness  necessary  to  be  given 
walls  depends  upon  the  height,  length,  and  pressure  of  the  load, 
wind,  etc.,  and  may  be  determined  from  that  section  of  applied  me- 
chanics termed  ''Stability  of  Structures."  In  practice,  however, 
these  calculations  are  rarely  made  except  for  the  most  important 


90  MASONRY  CONSTRUCTION 


structures,  for  the  reason  that  if  a  vertical  wall  be  properly  con- 
structed upon  a  sufficient  foundation,  the  combined  mass  will  retain 
its  position,  and  bear  pressure  acting  in  the  direction  of  gravity,  to 
any  extent  that  the  ground  on  which  it  stands  and  the  component 
materials  will  sustain.  But  pressure  acting  .laterally  has  a  tendency 
to  overturn  the  wall,  and  therefore  it  must  be  the  aim  of  the  con- 
structor to  compel  as  far  as  possible,  all  forces  that  can  act  upon  an 
upright  wall  to  act  in  the  direction  of  gravity. 

In  determining  thickness  of  walls  the  following  general  prin- 
ciples must  be  recognized : 

1.  That  the  center  of  pressure  (a  vertical  line  through  the  center 
of  gravity  of  the  weight),  shall  pass  through  the  center  of  the  area  of 
the  foundation.     If  the  axis  of  pressure  does  not  coincide  exactly 
with  the  axis  of  the  base,  the  ground  will  yield  most  on  the  side  which 
is  pressed  most ;  and  as  the  ground  yields,  the  base  assumes  an  inclined 
position,  and  carries  the  lower  part  of  the  structure  with  it,  producing 
cracks,  if  nothing  more. 

2.  That  the  length  of  a  wall  is  a  source  of  weakness  and  that 
the  thickness  should  be  increased  at  least  4  inches  for  every  25  feet 
over  100  feet  in  length. 

3.  That  high  stories  and  clear  spans  exceeding  25  feet  require 
thick  walls. 

4.  That  walls  of  warehouses  and  factories  require  a  greater 
thickness  than  those  used  for  dwellings  or  offices. 

5.  That  walls  containing   openings  to  the  extent   of   33  per 
cent  of  the  area  should  be  increased  in  thickness. 

6.  That  a  wall  should   never   be    bonded    into    another   wall 
either  much  heavier  or  lighter  than  itself. 

In  nearly  all  of  the  larger  cities  the  minimum  thickness  of  walls 
is  prescribed  by  ordinance. 

The  accompanying  table  gives  the  more  usual  dimensions: 


MASOMEY  CONSTRUCTION 


91 


>  .a  ®  ?3  03  3 

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•w  g  -g  >>+*  as 

O  3;  W  f->  o3  . 


S^^la 

|1H*! 

IlIHI 


s 

03  ^ 


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^  e*  co      co 


•  o  10  >o  o 

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cp 

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^000  O 

M   O   O  O  O 

•2  a  a  a  a 


a  a  a 

03  03  C3 


-III       1 
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O  O  10 
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Zg 


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92 


MASONRY  CONSTRUCTION 


RETAINING  WALLS. 

A  retaining  wall  is  a  wall  built  for  the  purpose  of  "retaining" 
or  holding  up  earth  or  water.  In  engineering  practice  such  walls 
attain  frequently  large  proportions,  being  used  in  the  construction  of 
railroads,  docks,  waterworks,  etc. 

The  form  of  cross-section  varies  considerably  according  to  cir- 
cumstances, and  often  according  to  the  fancy  of  the  designer.  The 


Fig.  23. 


r 


Fig.  24. 


Fig.  25. 


more  usual  forms  are  shown  in  Figs.  22  to  25.  The  triangular  section 
is  the  one  which  is  theoretically  the  most  economical,  and  the  nearer 
that  practical  consideration  will  allow  of  its  being  conformed  to 
the  better. 

All  other  tilings  being  equal,  the  greater  the  face  batter  the 
greater  will  be  the  stability  of  the  wall ;  but  considerations  connected 
with  the  functions  of  the  wall  limit  the  full  application  of  this  con- 
dition, and  walls  are  usually  constructed  with  only  a  moderate  batter 
on  the  face,  the  <liminution  towards  the  top  being  obtained  by  a  back 


MASONRY  CONSTRUCTION  93 

batter  worked  out  in  a  series  of  offsets.  Walls  so  designed  contain 
no  more  material  and  present  greater  resistance  to  overturning  than 
walls  with  vertical  backs. 

Dry  stone  retaining  walls  are  best  suited  for  roads  on  account  of 
their  self-draining  properties  and  their  cheapness.  If  these  dry  walls 
are  properly  filled  in  behind  with  stones  and  chips,  they  are,  if  well 
constructed,  seldom  injured  or  overthrown  by  pressure  from  behind. 
If  the  stone  is  stratified  with  a  flat  cleavage,  the  construction  of  retain- 
ing and  parapet  walls  is  much  facilitated.  If  the  stone  has  no  natural 
cleavage,  great  care  is  necessary  to  obtain  a  proper  bond.  If  walls 
built  of  such  stone  are  of  coursed  rubble,  care  is  required  that  the 
masons  do  not  sacrifice  the  strength  of  the  walls  to  the  face  appearance. 
The  practice  of  building  walls  with  square  or  rectangular-faced 
stones,  tailing  off  behind,  laid  in  rows,  one  course  upon  the  other, 
the  rear  portions  of  the  walls  being  of  chips  and  rough  stones,  set 
anyhow,  cannot  .be  condemned  too  strongly.  Such  a  construction, 
which  is  very  common,  has  little  transverse  and  no  longitudinal 
strength. 

Little 'or  no  earth  should  be  used  for  back  filling  if  stone  is  avail- 
able. Where  earth  filling  is  used,  it  should  only  be  thrown  in  and 
left  to  settle  itself;  on  no  account  should  it  be  wetted  and  rammed. 

Thickness  of  Walls.  Retaining  walls  require  a  certain 
thickness  to  enable  them  to  resist  being  overthrown  by  the  thrust  of 
the  material  which  they  sustain.  The  amount  of  this  thrust  depends 
upon  the  height  of  the  mass  to  be  supported  and  upon  the  quality  of 
the  material. 

Surcharged  Walls,  A  retaining  wall  is  said  to  be  surcharged 
when  the  bank  it  retains  slopes  backwards  to  a  higher  level  than  the 
top  of  the  wall ;  the  slope  of  the  bank  may  be  either  equal  to  or  less, 
but  cannot  be  greater,  than  the  angle  of  repose  of  the  earth  of  the 
bank. 

Proportions  of  Retaining  Walls.  In  determining  the  pro- 
portions of  retaining  walls  experience,  rather  than  theory,  must  be 
our  guide.  The  proportions  will  depend  upon  the  character  of  the 
material  to  be  retained.  If  the  material  be  stratified  rock  with  inter- 
posed beds  of  clay,  earth,  or  sand,  and  if  the  strata  incline  toward 
the  wall,  it  may  require  to  be  of  far  greater  thickness  than  any  ordi- 
nary retaining  wall;  because  when  the  thin  seams  of. earth  become 


94  MASONRY  CONSTRUCTION 


softened  by  infiltrating  rain,  they  act  as  lubricants,  like  soap  or  tallow, 
to  facilitate  the  sliding  of  the  rock  strata;  and  thus  bring  an  enormous 
pressure  against  the  wall.  Or  the  rock  may  be  set  in  motion  by  the 
action  of  frost  on  the  clay  seams.  Even  if  there  be  no  rock,  still  if 
*he  strata  of  soil  dip  toward  the  wall,  there  will  always  be  danger 
of  a  similar  result;  and  additional  precautions  must  be  adopted, 
especially  when  the  strata  reach  to  a  much  greater  height  than 
the  wall. 

The  foundation  of  retaining  walls  should  be  particularly  secure; 
the  majority  of  failures  which  have  occurred  in  such  walls  have  been 
due  to  defective  foundations. 

Failure  of  Retaining  Walls.  Retaining  walls  generally  fail 
(1)  by  overturning  or  by  sliding,  or  (2)  by  bulging  out  of  the  body  of 
the  masonry.  Sliding  may  be  prevented  by  inclining  the  courses 
inward.  An  objection  to  this  inclination  of  the  joints  in  dry  walls 
is  that  rainwater,  falling  on  the  battered  face,  is  thereby  carried 
inwards  to  the  earth  backing,  which  thus  becomes  soft  and  settles. 
This  objection  may  be  overcome  by  using  mortar  in  the  face  joints 
to  the  depth  of  a  foot,  or  by  making  the  face  of  the  wall  nearly 
vertical. 

Protection  of  Retaining  Walls.  The  top  of  the  walls 
should  be  protected  with  a  coping  of  large  heavy  stones  laid  as  headers. 

Where  springs  occur  behind  or  below  the  wall,  they  must  be 
carried  away  by  piping  or  otherwise  got  rid  of. 

The  back  of  the  wall  should  be  left  as  rough  as  possible,  so  as 
to  increase  the  friction  of  the  earth  against  it. 

Weep  Holes.  In  masonry  walls,  weep  holes  must  be  left  at 
frequent  intervals,  in  very  wet  localities  as  close  as  4  feet,  so  as  to 
permit  the  free  escape  of  any  water  which  may  find  its  way  to  the 
back  of  the  wall.  These  holes  should  be  about  2  inches  wide  and 
should  be  backed  with  some  permeable  material,  such  as  gravel, 
broken  stone,  etc. 

Formula  for  Calculating  Thickness  of  Retaining  Walls. 
E  =  weight  of  earthwork  per  cubic  yard. 
W=weight  of  wall  per  cubic  yard. 
H  —  height  of  wall. 
T  =  thickness  of  wall  at  top. 
T  =  H  X  tabular  number  (Table  12). 


MASONRY  CONSTRUCTION 


95 


TABLE  12. 
Coefficients  for  Retaining  Walls. 


E  :  W  :  :  1  :  5 

E  :  W::l  :4 

Clay. 

Sand. 

Clay. 

Sand. 

1  in  4 

.083 

.029 

.115 

.054 

1  in  5 

.122 

.065 

.155 

.092 

1  in  6 

.149 

.092 

.183 

.118 

1  in  8 

.184 

..125 

.218 

.153 

1  in  12 

.221 

.160 

.256 

.189 

Vertical 

.300 

.239 

336 

.267 

Retaining  walls  of  dry  stone  should  not  be  less  than  3  feet  thick 
at  top,  with  a  face  batter  of  1  in  4  and  back  perpendicular,  the  courses 
laid  perpendicular  to  the  face  batter.  Weep  holes  are  unnecessary 
unless  the  walls  are  in  very  wet  situations. 

Retaining  walls  of  masonry  should  be  at  least  2  feet  thick  at  top, 
back  perpendicular  and  face  battered  at  the  rate  of  1  in  6. 

Surcharged  Walls.     In  calculating  the  strength  of  surcharged 
walls  substitute  Y  for  H,  Y  being  the  perpendicular  at  the  end  of  a 
line,  L  =  H  measured  along  the  slope  to  be  retained  (Fig.  26).- 
Y==  1.7IH  in  slopes  of  1     :1; 
=  1.55H  "       "       "'I-}:!; 
=  1.35H  "       "      "2:1; 
ai  1.31H  "       "       "3:1; 
=  1.24H  "       "       "  4    : 1. 

DESCRIPTION  OF  ARCHES. 

Basket = Han  die  Arch  :  One  in  which  the  intrados  resembles 
a  semi-ellipse,  but  is  composed  of  arcs  of  circles  tangent  to  each  other 

Circular  Arch  :     One  in  which  the  intrados  is  a  part  of  a  circle. 

Discharging  Arch  :  An  arch  built  above  a  lintel  to  take  the 
superincumbent  pressure  therefrom. 

Elliptical  Arch  :  One  in  which  the  intrados  is  a  part  of  an 
ellipse. 

Qeostatic  Arch:  An  arch  in  equilibrium  under  the  vertical 
pressure  of  an  earth  embankment. 

Hydrostatic  Arch  :  An  arch  in  equilibrium  under  the  vertical 
pressure  of  water 


90  MASONRY  CONSTRUCTION 


Inverted  Arches  are  like  ordinary  arches,  but  are  built  with 
the  crown  downwards.  They  are  generally  semicircular  or  segmental 
in  section,  and  are  used  chiefly  in  connection  with  foundations. 

Plain  or  Rough  Arches  are  those  in  which  none  of  the  bricks 
are  cut  to  fit  the  splay.  Hence  the  joints  are  quite  close  to  each  other 
at  the  soffit,  and  wider  towards  the  outer  curve  of  the  arch ;  they  are 
generally  used  as  relieving  <nnl  trimrr  arches^  for  tunnd  lining, 
and  all  arches  where  strength  is  essential  and  appearance  no  par- 
ticular object.  In  constructing  arches  of  this  kind  it  is  usual  to  form 
them  of  two  or  more  four-inch  concentric  rings  until  the  required 
thickness  is  obtained.  Each  of  the  successive  rings  is  built  inde- 
pendently, having  no  connection  with  the  others  beyond  the  adhesion 
of  the  mortar  in  the  ring  joint.  It  is  necessary  that  each  ring  should 
be  finished  before  the  next  is  commenced;  also  that  each  course  be 
bonded  throughout  the  length  of  the  arch,  and  that  the  ring  joint 
should  be  of  a  regular  thickness.  For  if  one  ring  is  built  with  a  thin 
joint  and  another  with  a  thick  one  the  one  having  the  most  mortar  will 
shrink,  causing  a  fracture  and  depriving  the  arch  of  much  of  its 
strength. 

Pointed  Arch  :  One  in  which  the  intrados  consists  of  two  arcs 
of  equal  circles  intersecting  over  the  middle  of  the  span. 

Relieving  Arch  :     See  Discharging  Arch. 

Right  Arch :  A  cylindrical  arch  either  circular  or  elliptical, 
terminated  by  two  planes,  termed  heads  of  the-  arch,  at  right  angles 
to  the  axis  of  the  arch. 

Segmental  Arch:     One  whose  intrados  is  less  than  a  semicircle. 

Semicircular  Arch:  One  whose  intrados  is  a  semicircle;  also 
called  a  full-centered  arch. 

SKew  Arch  :  One  whose  heads  are  oblique  to  the  axis.  Skew 
arches  are  quite  common  in  Europe,  but  are  rarely  employed  in  the 
I'nited  States;  and  in  the  latter  when  an  oblique  arch  is  employed  it 
is  usually  made,  not  after  the  European  method  with  spiral  joints, 
but  by  building  a  number  of  short  right  arches  or  ribs  in  contact  with 
each  other,  each  successive  rib  being  placed  a  little  to  one  side  of  its 
neighbor. 

DEFINITIONS  OF  PARTS  OF  ARCHES. 

Abutment :  The  outer  wall  that  supports  the  arch,  and  which 
connects  it  to  the  adjacent  banks. 


MASONRY  CONSTRUCTION  97 


Arch  Sheeting  :  The  voussoirs  which  do  not  show  at  the  end 
of  the  arch. 

Camber  is  a  slight  rise  of  an  arch,  as  J  to  J  inch  per  foot 
of  span. 

Crown  :    The  highest  point  of  the  arch. 

Extrados  :     The  upper  and  outer  surface  of  the  arch. 

Haunches  :  The  sides  of  the  arch  from  the  springing  line  half 
way  up  to  the  crown. 

Heading  Joint :  A  joint  in  a  plane  at  right  angles  to  the  axis 
of  the  arch.  It  is  not  continuous. 

Intrados  or  Soffit :     The  under  or  lower  surface  of  the  arch. 

Invert :  An  inverted  arch,  one  with  its  intrados  below  the  axis 
or  springing  line;  e.g.,  the  lower  half  of  a  circular  sewer. 

Keystone  :     The  center  voussoir  at  the  crown. 

Length  :     The  distance  between  face  stones  of  the  arch. 

Pier :     The  intermediate  support  for  two  or  more  arches. 

Ring  Course :     A  course  parallel  to  the  face  of  the  arch. 

Ring  Stones :  The  voussoirs  or  arch  stones  which  show  at 
the  ends  of  the  arch. 

Rise :  The  height  from  the  springing  line  to  under  side  of  the 
arch  at  the  keystone. 

Skew  Back :  The  upper  surface  of  an  abutment  or  pier  from 
which  an  arch  springs;  its  face  is  on  a  line  radiating  from  the 
center  of  the  arch. 

Span :  The  horizontal  distance  from  springing  to  springing  of 
the  arch. 

Spandrel :  The  space  contained  between  a  horizontal  line 
drawn  through  the  crown  of  the  arch  and  a  vertical  line  drawn  through 
the  upper  end  of  the  skew  back. 

Springing :     The  point  from  which  the  arch  begins  or  springs. 

Springer :     The  lowest  voussoir  or  arch  stone. 

String  Course :  A  course  of  voussoirs  extending  from  one 
end  of  the  arch  to  the  other. 

Voussoirs :     The  blocks  forming  the  arch. 

Arches:  The  arch  is  a  combination  of  wedge-shaped  blocks, 
termed  arch  stones,  or  voussoirs,  truncated  towards  the  angle  of  the 
wedges  by  a  curved  surface  which  is  usually  normal  to  the  surfaces 


98  MASONRY  CONSTRUCTION 


of  the  joints  between  the  blocks.  This  inferior  surface  of  the  arch 
is  termed  the  soffit.  The  upper  or  outer  surface  of  the  arch  is  termed 
the  back. 

The  extreme  blocks  of  the  arch  rest  against  lateral  supports, 
termed  abutments,  which  sustain  both  the  vertical  pressure  arising 
from  the  weight  of  arch  stones,  and  the  weight  of  whatever  lies  upon 
them;  also  the  lateral  pressure  caused  by  the  action  of  the  arch. 

The  forms  of  an  arch  may  be  the  semicircle,  the  segment,  or  a 
compound  curve  formed  of  a  number  of  circular  curves  of  different 
radii.  Full  center  arches,  or  entire  semicircles,  offer  the  advantages 
of  simplicity  of  form,  great  strength,  and  small  lateral  thrust;  but  if 
the  span  is  large  they  require  a  correspondingly  great  rise,  which  is 
often  objectionable.  The  flat  or  segmental  arch  enables  us  to  reduce 
the  rise,  but  it  throws  a  great  lateral  strain  upon  the  abutments.  The 
compound  curve  gives,  when  properly  proportioned,  a  strong  arch 
with  a  moderate  lateral  action,  is  easily  adjustable  to  different  ratios 
between  the  span  and  the  rise,  and  is  unsurpassed  in  its  general 
appearance.  In  striking  the  compound  curve,  the  following  con- 
ditions are  to  be  observed:  The  tangents  at  the  springing  must  be 
vertical,  the  tangent  at  the  crown  horizontal,  and  the  number  of 
centers  must  be  uneven,  curves  of  3  and  5  centers  will  be  found-  to 
fulfil  all  requirements. 

In  designing  an  arch  the  first  step  is  to  determine  the  thickness 
at  the  crown,  i.e.,  the  depth  of  the  keystone.  This  depth  depends 
upon  the  form,  and  rise  of  the  arch,  the  character  of  the  masonry, 
and  the  quality  of  the  stone;  and  is  usually  determined  by  Trautwine's 
formula,  which  is  as  follows  for  a  first-class  cut  stone  arch  whether 
circular  or  elliptical. 


in  which 

D  =  the  depth  at  the  crown  in  feet. 
R  =  the  radius  of  curvature  of  the  intrados  in  feet. 
S  —  the  span  in  feet. 

For  second-class  work,  the  depth  found  by  this  formula  may  be 
increased  about  one-eighth  part;  and  for  brickwork  or  fair  rubble, 
about  one-third. 


MASONRY  CONSTRUCTION 


99 


Table  13  gives  the  depth  of  keystone  for  semicircular  arches, 
the  second  column  being  for  hammer-dressed  beds,  the  third  for  beds 
roughly  dressed  with  the  chisel,  and  the  fourth  for  brick  masonry. 


TABLE  13. 


Thickness  of  Arch  in  inches. 


Span  in  feet. 

First-class  Masonry. 

Second-class  Masonry 

Brick  Masonry. 

6 

12 

15 

12 

8 

13 

16 

16 

10 

14 

17 

20 

12 

15 

19 

20 

14 

16 

20 

24 

16 

17 

21 

24 

18 

18 

23 

24 

20 

19 

24 

24 

25 

20 

25 

28 

30 

21 

26 

28 

35 

22 

28 

28 

40 

23 

29 

32 

45 

24 

30 

32 

50 

25 

31 

32 

Thickness  of  Arch  at  the  Springing.  Generally  the  thick- 
ness of  the  arch  at  the  springing  is  found  by  an  application  of 
theory. 

If  the  loads  are  vertical,  the  horizontal  component  of  the 
compression  on  the  arch  is  constant;  and  hence,  to  have  the 
mean  pressure  on  the  joints  uniform,  the  vertical  projection  of  the 
joints  should  be  constant.  This  principle  leads  to  the  following 
formula: 

The  length  measured  radially  of  each  joint  between  the  joint  of 
rupture  and  the  crown  should  be  such  that  its  vertical  projection  is  equal 
to  the  depth  of  the  keystone. 

The  length  of  the  joint  of  rupture,  i.e.,  the  thickness  of  the  arch 
at  the  practical  springing  line,  can  be  computed  by  the  formula 

z  =  d  sec  a 

in  which  z  is  the  length  of  the  joint, 
d  the  depth  of  the  crown, 
a  the  angle  the  joint  makes  with  the  vertical. 
The  following  are  the  values  for  circular  and  segmental  arches: 


100  MASONRY  CONSTRUCTION 


If  —-  >  ~,  I  =  2.00  d 
"~  =  ~,  l=lMd 


in  which  R  =  the  rise,  in  feet 
S  =  the  span,  in  feet. 

Thickness  of  the  Abutments,  The  thickness  of  the  abut- 
ment is  determined  by  the  following  formula: 

t  =  0.2  p  +  0.1  R  +  2.0 

in  which  t  is  the  thickness  of  the  abutment  at   the  springing,  p  the 
radius,  and  R  the  rise  —  all  in  feet. 

The  above  formula  applies  equally  to  the  smallest  culvert  or  the 
largest  bridge  —  whether  circular  or  elliptical,  and  whatever  the  pro- 
portions of  rise  and  span  —  and  to  any  height  of  abutment. 

Table  14  gives  the  minimum  thickness  of  abutments  for  arches 
of  120  degrees  where  the  depth  of  crown  does  not  exceed  3  feet. 

Calculated  from  the  formula 


T 
= 


in  which  D  =  depth  or  thickness  of  crown  in  feet; 

H  =  height  of  abutment  to  springing  in  feet; 

R  =  radius  of  arch  at  crown  in  feet; 

T  =  thickness  of  abutment  in  feet. 

Arches  fail  by  the  crown  falling  inward,  and  thrusting  outward 
the  lower  portions,  presenting  five  points  of  rupture,  one  at  the  key- 
stone, one  on  each  side  of  it  which  limit  the  portions  that  fall  inward, 
and  one  on  each  side  near  the  springing  lines  which  limit  the  parts 
thrust  outward.  In  pointed  arches,  or  those  in  which  the  rise  is 
greater  than  half  the  span,  the  tending  to  yielding  is,  in  some  cases, 
different;  and  thrust  upward  and  outward  the  parts  near  the  crown. 


MASONRY  CONSTRUCTION 


101 


TABLE  14. 

Minimum  Thickness  of  Abutments  for  Arches   of   120   Degrees 
Where  the  Depth  of  Crown  Does  Not  Exceed  3  Feet. 


Span  of 


Height  of  Abutment  to  Springing,  in  feet. 


Arch. 

5 

7.5 

10 

20 

30 

8  feet 

3.7 

4.2 

4.3 

4.6 

4.7 

9    " 

3.9 

4.4 

4.6 

4.9 

5.0 

10    " 

4.2 

4.6 

4.8 

5.1 

5.2 

12 

4.5 

4.7 

5.2 

5.6 

5.7 

14 

4.7 

5.2 

5.5 

6.0 

6.1 

16 

4.9 

5.5 

5.8 

6.4 

6.5 

18 

5.1 

5.8 

6.1 

6.7 

6.9 

20 

5.3 

6.0 

6.4 

7.1 

7.2 

22 

5.5 

6.2 

6.6 

7.3 

7.6 

24 

5.6 

6.4 

6.9 

7.6 

7.9 

30 

6.0 

7.0 

7.5 

8.4 

8.8 

40 

6.5 

7.7 

8.4 

9.6 

10.0 

50 

6.9 

8.2 

9.1 

10.5 

11.1 

60 

7.2 

8.7 

9.7 

11.4 

1-2.0 

70 

7.4 

9.1 

10.2 

11.8 

12.9 

80 

7.6 

9.4 

10.6 

12.8 

13.6 

90 

7.8 

9.7 

11.0 

13.4 

14.3 

100 

7.9 

10.0 

11.4 

14.0 

15.0 

NOTE.  The  thickness  of  abutment  for  a  semicircular  arch  may  be  taken  from  the 
above  table  by  considering  it  as  approximately  equal  to  that  for  an  arch  of  120  degrees 
having  the  same  radius  of  curvature;  therefore  by  dividing  the  span  of  the  semicircular 
arch  by  1.155  it  will  give  the  span  of  the  120-degree  arch  requiring  the  same  thickness  of 
abutment. 

The  angle  which  a  line  drawn  from  the  center  of  the  arch  to  the 
joint  of  rupture  makes  with  a  vertical  line  is  called  the  angle  of  rupture. 
This  term  is  also  used  when  the  arch  is  stable,  or  where  there  is  no 
joint  of  rupture,  in  which  case  it  refers  to  that  point  about  which  there 
is  the  greatest  tendency  to  rotate.  It  may  also  be  defined  as  including 
that  portion  of  the  arch  near  the  crown  which  will  cause  the  greatest 
thrust  or  horizontal  pressure  at  the  crown.  This  thrust  tends  to 
crush  the  voussoirs  at  the  crown,  and  also  to  overturn  the  abutments 
about  some  outer  joint.  In  very  thick  arches  rupture  may  take  place 
from  slipping  of  the  joints. 

In  order  to  avoid  any  tendency  of  the  joints  to  open,  the  arch 
should  be  so  designed  that  the  actual  resistance  line  shall  everywhere 
be  within  the  middle  third  of  the  depth  of  the  arch  ring. 

In  general  the  design  of  an  arch  is  reached  by  a  series  of  approx- 
imations. Thus,  a  form  of  arch  and  spandrel  must  be  assumed  in 


102 


MASONRY  CONSTRUCTION 


advance  in  order  to  find  their  common  center  of  gravity  for  the  pur- 
pose of  determining  the  horizontal  thrust  at  the  crown,  and  the 
reaction  at  the  skewback. 

Backing.     The  backing  is  masonry  of  inferior  quality  or  con- 
crete, laid  outside  and  above  the  arch  stones  proper,  to  give  additional 


Fig.  26.    Rowlock  Bond. 


Fig.  27.    Rowlock  with  Skewback. 


Fig.  28.    Block  in  Course  Bond. 


Fig.  29.    Header  and  Stretcher. 


Fig.  30.    Flat  Arch.  Fig.  31.    Relieving  Arch. 

security.     Ordinarily,  the  backing  has  a  zero  thickness  at  or  near 
the  crown,  and  gradually  increases  to  the  upringing  line. 

Spandrel    Filling.     Since    the  surface  of    the  roadway  must 
not  deviate  from  a  horizontal  line,  a  considerable  quantity  of  material 


MASONRY  CONSTRUCTION  103 


is  required  above  the  backing  to  bring  the  roadway  level.  Ordinarily 
this  space  is  filled  with  earth,  gravel,  broken  stone,  cinders,  etc. 
Sometimes  to  save  filling  small  arches  are  built  over  the  haunches 
of  the  main  arch. 

Drainage.  The  drainage  of  arcn  bridges  of  more  than  one 
span  is  generally  effected  by  giving  the  top  surface  of  the  backing  a 
slight  inclination  from  each  side  toward  the  center  of  the  width  of  the 
bridge  and  also  from  the  center  toward  the  end  of  the  span.  The 
water  is  thus  collected  over  the  piers,  from  whence  it  is  discharged 
through  pipes  laid  in  the  masonry. 

To  prevent  leakage  through  the  backing  and  through  the  arch 
sheeting,  the  top  of  the  former  should  be  covered  with  a  layer  of 
puddle,  or  plastered  with  a  coat  of  cement  mortar,  or  painted  with 
coal  tar  or  asphaltum. 

Brick  Arches.  The  only  matter  requiring  special  mention  in 
connection  with  brick  arches  is  the  bond  to  be  employed.  When 
the  thickness  of  the  arch  exceeds  a  brick  and  a  half,  the  bond  from 
the  soffit  outward  is  a  very  important  matter.  There  are  three 
principal  methods  employed  in  bonding  brick  arches:  (1)  The  arch 
may  be  built  in  concentric  rings;  i.e.,  all  the  brick  may  be  laid  as 
stretchers,  with  only  the  tenacity  of  the  mortar  to  unite  the  several 
rings.  This  method  is  called  rowlock  bond:  (2)  Part  of  the  brick 
may  be  laid  as  stretchers  and  part  as  headers,  by  thickening  the  outer 
ends  of  the  joints — either  by  using  more  mortar  or  by  driving  in  thin 
pieces  of  slate,  so  that  there  shall  b3  the  same  number  of  brick  in 
each  ring.  This  form  of  construction  is  called  header  and  stretcher 
bond:  (3)  Block  in  course  bond  is  formed  by  dividing  the  arch  into 
sections  similar  in  shape  to  the  voussoirs  of  stone  arches,  and  laying 
the  brick  in  each  section  with  any  desired  bond. 

Skewback,  In  brick  arches  of  large  span  a  stone  skewback 
is  used  for  the  arch  to  spring  from.  The  stone  should  be  cut  so  as 
to  bond  into  the  abutment,  and  the  springing  surface  should  be  cut 
to  a  true  plane,  radiating  from  the  center  from  which  the  arch  is 
struck. 

Flat  Arches  are  often  built  over  door  or  window  openings; 
they  are  always  liable  to  settle  and  should  be  supported  by  an 
angle  bar,  the  vertical  flange  of  which  may  be  concealed  behind 
the  arch. 


104  MASONRY  CONSTRUCTION 

Relieving  Arches.  This  term  is  applied  to  arches  turned 
over  openings  in  walls  to  support  the  wall  above;  beams  called  lintels 
are  usually  used  in  connection  with  this  type  of  arch,  the  lintel  should 
not  have  a  bearing  on  the  wall  of  more  than  4  inches,  and  the  arch 
should  spring  from  beyond  the  ends  of  the  lintel  as  shown  in  A,  Fig.  31, 
and  not  as  at  B. 

CONSTRUCTION  OF  ARCHES. 

In  constructing  ornamental  arches  of  small  span  the  bricks 
should  be  cut  and  rubbed  with  great  care  to  the  proper  splay  or  wedge 
like  form  necessary,  and  according  to  the  gauges  or  regularly  measured 
dimensions. 

This  is  not  always  done,  the  external  course  only  being  rubbed, 
so  that  the  work  may  have  a  pleasing  appearance  to  the  eye,  while 
the  interior,  which  is  hidden  from  view,  is  slurred  over,  and  in  order 
to  save  time  many  of  the  interior  bricks  are  apt  to  be  so  cut  away  as 
to  deprive  the  arch  of  its  strength.  This  class  of  work  produces 
cracks  and  causes  the  arch  to  bulge  forward,  and  may  cause  one  of 
the  bricks  of  a  straight  arch  to  drop  down  lower  than  the  soffit. 

In  setting  arches  the  mason  should  be  sure  that  the  centers  are 
set  level  and  plumb,  that  the  arch  brick  or  stone  may  rest  upon  them 
square.  When  the  brick  or  stone  are  properly  cut  beforehand  the 
courses  can  be  gauged  upon  the  center  from  the  key  downwards. 
The  soffit  of  each  course  should  fit  the  center  perfectly. 

The  mortar  joints  should  b?  as  thin  as  possible  and  well  flushed  up. 

In  setting  the  face  stones  it  is  necessary  to  have  a  radius  line,  and 
draw  it  up  and  test  the  setting  of  each  stone  as  it  is  laid. 

The  framing,  setting  up,  and  striking  of  the  centers  are  very 
important  parts  of  the  construction  of  any  arch,  particularly  one 
of  long  span.  A  change  in  the  shape  of  the  center,  due  to  insufficient 
strength  or  improper  bracing,  will  be  followed  by  a  change  in  the 
curve  of  the  intrados,  and  consequently  of  the  line  of  resistance, 
which  may  endanger  the  safety  of  the  arch  itself. 

CENTERING  FOR  ARCHES. 

No  arch  becomes  self-supporting  until  keyed  up,  that  is,  until 
the  crown  or  keystone  course  is  laid.  Until  that  time  the  arch  ring, 
which  should  be  built  up  simultaneously  from  both  abutments,  has 


MASONRY  CONSTRUCTION 


105 


to  be  supported  by  frames  called  centers.  These  consist  of  a  series 
of  ribs  placed  from  3  to  6  or  more  feet  apart,  supported  from  below. 
The  upper  surface  of  these  ribs  is  cut  to  the  form  of  the  arch,  and  over 
these  a  series  of  planks  called  laggings  are  placed,  upon  which  the 
arch  stones  directly  rest.  The  ribs  may  be  of  timber  or  iron.  They 
should  be  strong  and  stiff.  Any  deformation  that  occurs  in  the  rib 
will  distort  the  arch,  and  may  even  result  in  its  collapse. 

Striking  the  Center.  The  ends  of  the  ribs  or  center  frames 
usually  rest  upon  a  timber  lying  parallel  to,  and  near,  the  springing 
line  of  the  arch.  This  tim- 
ber is  supported  by  wedges, 
preferably  of  hardwood,  rest- 
ing upon  a  second  stick,  which 
is  in  turn  supported  by  wooden 
posts,  usually  one  under  each 
end  of  each  rib.  The  wedges 
between  the  two  timbers,  as 
above,  are  used  in  removing 
the  center  after  the  arch  is 
completed,  and  are  known  as 
striking  wedges.  They  consist 
of  a  pair  of  folding  wedges,  1 
to  2  feet  long,  6  inches  wide, 
and  having  a  slope  of  from  1 
to  5  to  1  to  10,  placed  under 
each  end  of  each  rib.  It  is 
necessary  to  remove  the  cen- 
ters slowly,  particularly  for 
large  arches;  and  hence  the 
striking  wedges  should  have 
a  very  slight  taper,  the  larger  the  span  the  smaller  the  taper. 

The  center  is  lowered  by  driving  back  the  wedges.  To  lower 
the  center  uniformly  the  wedges  must  be  driven  back  uniformly. 
This  is  most  easily  accomplished  by  making  a  mark  on  the  side  of 
each  pair  of  wedges  before  commencing  to  drive,  and  then  moving 
each  the  same  amount. 

The  inclined  surfaces  of  the  wedges  should  be  lubricated  when 
the  center  is  set  up,  so  as  to  facilitate  the  striking. 


-  Weary  es  w"x/S"x  4- 

•  Temporary  Stone  Corbf/ 

Fig.  32.    Arch  Center. 


106  MASONRY  CONSTRUCTION 

Screws  may  be  used  instead  of  wedges  for  lowering  centers. 

Sand  is  also  employed  for  the  same  purpose.  The  method  fol- 
lowed is  to  support  the  center  frames  by  wooden  pistons  or  plungers 
resting  on  sand  confined  in  plate-iron  cylinders.  Near  the  bottom 
of  each  cylinder  there  is  a  plug  which  can  be  withdrawn  and  replaced 
at  pleasure,  thus  regulating  the  outflow  of  the  sand  and  the  descent 
of  the  center. 

There  is  great  difference  of  opinion  as  to  the  proper  time  for 
striking  centers.  Some  hold  that  the  center  should  be  struck  as 
soon  as  the  arch  is  completed  and  the  spandrel  filling  is  in  place; 
while  others  contend  that  the  mortar  should  be  given  time  to  harden. 
It  is  probably  best  to  slacken  the  centers  as  soon  as  the  keystone 
course  is  in  place,  so  as  to  bring  all  the  joints  under  pressure.  The 
length  of  time  which  should  elapse  before  the  centers  are  finally 
removed  should  vary  with  the  kind  of  mortar  employed  and  also 
with  its  amount.  In  brick  and  rubble  arches  a  large  proportion  of 
the  arch  ring  consists  of  mortar,  and  if  the  center  is  removed  too  soon 
the  compression  of  this  mortar  might  cause  a  serious  or  even  dangerous 
deformation  of  the  arch.  Hence  the  centers  of  such  arches  should 
remain  until  the  mortar  has  not  only  set,  but  has  attained  a  con- 
siderable part  of  its  ultimate  strength. 

Frequently  the  centers  of  bridge  arches  are  not  removed  for 
three  or  four  months  after  the  arch  is  completed,  but  usually  the 
centers  for  the  arches  of  tunnels,  sewers,  and  culverts  are  removed 
as  soon  as  the  arch  is  turned  and,  say,  half  of  the  spandrel  filling 
is  in  place. 

BRIDGE  ABUTMENTS. 

Form.  There  are  four  forms  of  abutment  in  use,  they  are  named 
according  to  their  form  as  the  straight  abutment,  the  wing  abutment, 
the  U  abutment  and  the  T  abutment. 

The  form  to  be  adopted  for  any  particular  case  will  depend 
upon  the  location — whether  the  banks  are  low  and  flat,  or  steep  and 
rocky,  whether  the  current  is  swift  or  slow,  and  also  upon  the  relative 
cost  of  earthwork  and  masonry.  Where  a  river  acts  dangerously 
upon  a  shore,  wing  walls  will  be  necessary.  These  wings  may  be 
curved  or  straight.  The  slope  of  the  wings  may  be  finished  with  an 
inclined  coping,  or  offset  at  each  course.  Wing  walls  subjected  to 


MASONRY  CONSTRUCTION 


107 


108 


MASONRY  CONSTRUCTION 


FronT. 


PA.   M     m     VA     U     U     j.j    1:1     ti     l<\     f:J     SI     N     f)     ii     1. 1     M 
Stringer  1  coping 


Eie  vat/on. 


Foundation 


1 


Foundation. 


Plan 
Fig.  34.    Abutment  for  Railroad  Bridge. 


MASONRY  CONSTRUCTION  109 

special  strains,  or  to  particular  currents  of  water  require  positions 
and  forms  accordingly. 

The  abutment  of  a  bridge  has  two  offices  to  perform;  (1)  to 
support  one  end  of  the  bridge,  and  (2)  to  keep  the  earth  embankment 
from  sliding  into  the  water. 

The  abutment  may  fail  (1)  by  sliding  forward,  (2)  by  bulging, 
or  (3)  by  crushing. 

The  dimensions  of  abutments  will  vary  with  each  case,  with 
the  form  and  size  of  the  bridge  and  with  the  pressure  to  be  sustained ; 
the  dimensions  may  be  determined  by  the  same  formulas  as  used 
for  retaining  walls. 

For  railroad  bridges  the  top  dimensions  are  usually  5  feet  wide 
by  20  feet  long.  The  usual  batter  is  1  in  12,  for  heights  under  20 
feet  the  top  dimensions  and  the  batter  determine  the  thickness  at  the 
bottom.  For  greater  heights,  the  uniform  rule  is  to  make  the  thick- 
ness four-tenths  the  height. 

Bridge  abutments  are  built  of  first  or  second-class  masonry  or 
of  concrete  alone  or  faced  with  stone  masonry,  according  to  the  im- 
portance and  location  of  the  structure. 

BRIDGE  PIERS. 

The  thickness  of  a  pier  for  simply  supporting  the  weight  of  the 
superstructure  need  be  but  very  little  at  the  top,  care  being  taken  to 
secure  a  sufficient  bearing  at  the  foundation.  Piers  should  be  thick 
enough,  however,  to  resist  shocks  and  lateral  strains,  not  only  from 
a  passing  load,  but  from  floating  ice  and  ice  jams;  and  in  rivers  where 
a  sandy  bottom  is  liable  to  deep  scouring,  so  that  the  bottom  may 
work  out  much  deeper  on  one  side  of  a  pier  than  on  the  other,  regard 
should  be  paid  to  the  lateral  pressure  thus  thrown  on  the  pier.  For 
mere  bearing  purposes  the  following  widths  are  ample  for  first-class 
masonry — span  50  feet,  width  4  feet,  span  200  feet,  width  7  feet. 
Theoretically  the  dimensions  at  the  bottom  are  determined  by  the 
area  necessary  for  stability;  but  the  top  dimensions  required  for  the 
bridge  seat,  together  with  the  batter,  1  in  12  or  1  in  24,  generally 
make  the  dimensions  of  the  base  sufficient  for  stability. 

The  up-stream  end  of  a  pier,  and  to  a  considerable  extent  the 
down-stream  end  also,  should  be  rounded  or  pointed  to  serve  as  a 
cutwater  to  turn  the  current  aside  and  to  prevent  the  formation  of 


110 


MASONRY  CONSTRUCTION 


whirls  which  act  upon  the  bed  of  the  stream  around  the  foundation, 
and  also  to  form  a  fender  to  protect  the  pier  proper  from  being  dam- 
aged by  ice,  tugs,  boats,  etc.  This  rounding  or  pointing  is  designated 
by  the  name  starling,  the  best  form  appears  to  be  a  semi-ellipse. 
The  distance  to  which  they  should  extend  from  the  pier  depends 
upon  local  circumstances. 

A  bridge  pier  may  fail  in  any  one  of  these  ways;  (1)  by  sliding 
on  any  section  on  account  of  the  action  of  the  wind   against  the  ex- 


—B 


C— 


J-                                          -I 

«  39-  * 

1 

i 

--D 


Chcrnnei  P/ers 


Fig.  35.    Type  of  Bridge  Pier. 

posed  part  of  the  pier;  (2)  by  overturning  at  any  section  where  the 
moment  of  the  horizontal  forces  above  the  section  exceeds  the  moment 
of  the  weight  of  the  section ;  or  (3)  by  crushing  at  any  section  under 
the  combined  weight  of  the  pier,  the  bridge  and  the  load.  Bridge 
piers  are  usually  constructed  of  quarry-faced  ashlar  backed  with 


MASONRY  CONSTRUCTION 


111 


rubble  or  concrete.  Occasionally,  for  economy,  piers,  particularly 
pivot-piers,  are  built  hollow — sometimes  with  and  sometimes  without 
cross  walls. 

CULVERTS. 

Culverts  are  employed  for  conveying  under  a  railroad,  highway, 
or  canal  the  small  streams  crossed.  They  may  be  of  stone,  brick,  con- 
crete, earthenware,  or  iron  pipe  or  any  of  these  in  combination.  Two 
general  forms  of  masonry  culverts  are  in  use,  the  box  and  the  arch. 

Box  Culverts.  The  box  consists  of  vertical  side  walls  of 
masonry  with  flagstones  on  top  extending  from  one  wall  to  another. 

The  foundation  consists  of  large  stones  and  the  side  walls  may 
be  laid  dry  or  in  mortar. 


1 

\ 

I                       I 

&'$$& 

'<®>W$M>i§ 

IJU.Ul.Ul. 

$%%$&%/$$ 

!  .-- 

Fig.  36.    End  Elevation. 


Fig.  37.    Section  AB. 


1       1.1 


_J 


Fig.  38.    Plan. 


Fig.  39.    Section  CD. 
T  ypcs  of  Box  Culverts. 


The  paving  should  be  laid  independent  of  the  walls  and  should 
be  set  in  cement  mortar.  The  end  walls  are  finished  either  with  a 
plain  wall  perpendicular  to  the  axis  of  the  culvert  and  may  be  stepped, 
or  provided  with  wing  walls  as  the  circumstances  of  each  case  may 
require. 

The  thickness  of  the  cover  stone  may  be  determined  by  con- 
sidering it  as  a  beam  supported  at  the  ends  and  loaded  uniformly. 


112 


MASONRY  CONSTRUCTION 


Figs.  36  to  39  show  the  form  of  this  class  of  culverts  and  the 
dimensions  given  in  Table  15  will  serve  as  an  approximate  guide  for 
general  use. 

TABLE  15. 
Dimensions  for  Box  Culverts. 


Area. 

Opening. 

Side  Wall. 

Depth  of  Cover. 

Length  of  Cover. 

4  feet 

2'  X  2' 

2'  X  2' 

12  inches 

5  feet 

9     " 

3X3 

3X2* 

16       " 

6     " 

16    " 

4X4 

4X3 

20       " 

7     " 

25     " 

5X5 

5   X  3£. 

22       " 

8     " 

36     " 

6X6 

6X4 

24       " 

9    " 

Arch  Culverts.  The  dimensions  of  arch  culverts  are  deter- 
mined in  the  manner  described  herein  under  arches,  attention,  how- 
ever, being  given  to  the  following  points : 

Wing  Walls.  There  are  three  common  ways  of  arranging  the 
wing  walls  at  the  end  of  arch  culverts:  (1)  The  culvert  is  finished 
with  straight  walls  at  right  angles  to  the  axis  of  the  culvert.  (2)  The 
wings  are  placed  at  an  angle  of  30  degrees  with  the  axis  of  the  culvert. 
(3)  The  wing  walls  are  built  parallel  to  the  axis  of  the  culvert,  the 
back  of  the  wing  and  the  abutment  being  in  a  straight  line  and  the 
only  splay  being  derived  from  thinning  the  wings  at  their  outer  edge. 
The  most  economical  and  better  form  for  hydraulic  considerations 
is  the  second  form. 

Designing  Culverts.  In  the  design  of  culverts  care  is  required 
to  provide  an  ample  way  for  the  water  to  be  passed.  If  the  culvert 
is  too  small,  it  is  liable  to  cause  a  washout,  entailing  interruption  of 
traffic  and  cost  of  repairs,  and  possibly  may  cause  accidents  that  will 
require  the  payment  of  large  sums  for  damages.  On  the  other  hand, 
if  the  culvert  is  made  unnecessarily  large,  the  cost  of  construction  is 
needlessly  increased. 

The  area  of  waterway  required,  depends  (1)  upon  the  rate  of 
rainfall ;  (2)  the  kind  and  condition  of  the  soil ;  (3)  the  character  and 
inclination  of  the  surface;  (4)  the  condition  and  inclination  of  the  bed 
of  the  stream;  (5)  the  shape  of  the  area  to  be  drained,  and  the  position 
of  the  branches  of  the  stream;  (6)  the  form  of  the  mouth  and  the 
inclination  of  the  bed  of  the  culvert;  and  (7)  whether  it  is  permissible 


MASONRY  CONSTRUCTION 


113 


to  back  the  water  up  above  the  culvert,  thereby  causing  it  to  discharge 
under  a  head. 

(1)  The  maximum  rainfall  as  shown  by   statistics  is  about  one 

I 


Fig.  40.    Sectional  Elevation. 


I    .     I 


I    .     I 


I    .     I 


Fig.  41.    Plan. 


Fig.  42.     Section  AB. 


Fig.  43.    Section-CD. 
Type  of  Arch  Culvert. 


inch  per  hour  (except  during  heavy  storms),  equal  to  3,630  cubic  feet 
per  acre.  Owing  to  various  causes,  not  more  than  50  to  75  per  cent 
of  this  amount  will  reach  the  culvert  within  the  same  hour. 


114  MASONRY  CONSTRUCTION 

Inches  of  rainfall  X  3,630  =  cubic  feet  per  acre. 

Inches  of  rainfall  X  2,323,200  =  cubic  feet  per  square  mile. 

(2)  The  amount  of  water  to  be  drained  off  will  depend  upon 
the  permeability  of  the  surface  of  the  ground,  which  will  vary  greatly 
with,  the  kind  of  soil,  the  degree  of  saturation,  the  condition  of  the 
cultivation,  the  amount  of  vegetation,  etc. 

(3)  The  rapidity  with  which  the  water  will  reach  the  water- 
course depends  upon  whether  the  surface  is  rough  or  smooth,  steep 
or  flat,  barren  or  covered  with  vegetation,  etc. 

(4)  The  rapidity  with  which  the  water  will  reach  the  culvert 
depends  upon  whether  there  is  a  well-defined  and  unobstructed  chan- 
nel, or  whether  the  water  finds  its  way  in  a  broad  thin  sheet.     If  the 
watercourse  is  unobstructed  and  has  a  considerable  inclination,  the 
water  may  arrive  at  the  culvert  nearly  as  rapidly  as  it  falls;  but  if 
the  channel  is  obstructed,  the  water  may  be  much  longer  in  passing 
the  culvert  than  in  falling. 

(5)  The  area  of  the  waterway  depends  upon  the  amount  of  the 
area  to  be  drained ;  but  in  many  cases  the  shape  of  this  area  and  the 
position  of  the  branches  of  the  stream  are  of  more  importance  than 
the  amount  of  the  territory.     For  example,  if  the  area  is  long  and 
narrow,  the  water  from  the  lower  portion  may  pass  through  the 
culvert  before  that  from  the  upper  end  arrives;  or,  on  the  other  hand, 
if  the  upper  end  of  the  area  is  steeper  than  the  lower,  the  water  from 
the  former  may  arrive  simultaneously  with  that  from  the  latter. 
Again,  if  the  lower  part  of  the  area  is  better  supplied  with  branches 
than  the  upper  portion^  the  water  from  the  former  will  be  carried  past 
the  culvert  before  the  arrival  of  that  from  the  latter;  or,  on  the  other 
hand,  if  the  upper  portion  is  better  supplied  with  branch  watercourses 
than  the  lower,  the  water  from  the  whole  area  may  arrive  at  the  culvert 
at  nearly  the  same  time.     In  large  areas  the  shape  of  the  area  and 
the  position  of  the  watercourses  are  very  important  considerations. 

(6)  The  efficiency  of  a  culvert  may  be  materially  increased  by 
so  arranging  the  upper  end  that  the  water  may  enter  it  without  being 
retarded.     The  discharging  capacity  of  a  culvert  can  also  be  increased 
by  increasing  the  inclination  of  its  bed,  provided  the  channel  below 
will  allow  the  water  to  flow  away  freely  after  having  passed  the  culvert. 

(7)  The  discharging  capacity  of  a  culvert  can  be  greatly  in- 
creased by  allowing  the  water  to  dam  up  above  it.     A  culvert  will 


MASONRY  CONSTRUCTION  115 

discharge  twice  as  much  under  a  head  of  four  feet  as  under  a  head 
of  one  foot.  This  can  be  done  safely  only  with  a  well-constructed 
culvert. 

The  determination  of  the  values  of  the  different  factors  entering 
into  the  problem  is  almost  wholly  a  matter  of  judgment.  An  estimate 
for  any  one  of  the  above  factors  is  liable  to  be  in  error  from  100  to  200 
per  cent,  or  even  more,  and  of  course  any  result  deduced  from  such 
data  must  be  very  uncertain.  Fortunately,  mathematical  exactness 
is  not  required  by  the  problem  nor  warranted  by  the  data.  The 
question  is  not  one  of  10  or  20  per  cent  of  increase;  for  if  a  2-foot  pipe 
is  insufficient,  a  3-foot  pipe  will  probably  be  the  next  size,  an  increase 
of  225  per  cent;  and  if  a  6-foot  arch  culvert  is  too  small,  an  8-foot  will 
be  used,  an  increase  of  180  per  cent.  The  real  question  is  whether 
a  2-foot  pipe  or  an  8-foot  arch  culvert  is  needed. 

Calculating  Area  of  Waterway.  Numerous  empirical  for- 
mulas have  been  proposed  for  this  and  similar  problems;  but  at  best 
they  are  all  only  approximate,  since  no  formula  can  give  accurate 
results  with  inaccurate  data. 

The  size  of  waterway  may  be  determined  approximately  by 
the  following  formula: 


in  which 

Q  =  the  number  of  cubic  feet  per  acre  per  second  reaching  the 

mouth  of  the  culvert  or  drain. 
C  =  a  coefficient  ranging  from  .31  to  .75,  depending  upon  the 

nature  of  the  surface;  .62  is  recommended  for  general 

use. 
r  =  average  intensity  of  rainfall  in   cubic   feet  per  acre  per 

second. 

S  =  the  general  grade  of  the  area  per  thousand  feet. 
A  =  the  area  drained,  in  acres. 

CONCRETE  STEEL  MASONRY. 

Concrete  in  the  form  of  blocks  made  at  a  factory,  and  concrete 
formed  in  place  and  reinforced  by  steel  rods  and  bars  of  differing 
shapes  is  being  substituted  in  many  situations  for  stone  and  brick 
masonry.  For  the  construction  of  bridges  and  floors  it  is  extensively 


116 


MASONRY  CONSTRUCTION 


employed.  Several  systems  are  in  use,  each  known  by  the  name  of 
the  inventor.  Fi^.  44  shows  the  different  types  which  are  more  or 
less  popular. 

The  Monier  type  consists  of  a  mesh  work  of  longitudinal  and 
transverse  rods  of  steel,  usually  placed  near  the  center  line  of  the  arch 


Fig.  44.    Types  of  Concrete  Steel  Arches. 

rib.  This  type  rests  on  the  theory  that  the  steel  rods  will  resist  the 
compressive  stresses  of  the  rib,  while  the  concrete  acts  merely  as  a 
stiffener  to  prevent  the  steel  from  buckling, 

The  Melan  type  consists  of  steel  ribs  embedded  in  the  concrete 
and  extending  from  abutment  to  abutment.  The  ribs  are  in  the 
form  of  steel  I-beams  curved  to  follow  the  center  line  of  the  arch  rib. 
The  steel  is  assumed  to  be  sufficient  to  resist  the  bending  moments 
of  the  arch,  while  the  concrete  is  relied  upon  to  resist  the  thrust  and 
to  act  as  a  preservative  coating  for  the  steel. 

The  Von  Emperger  arch  is  a  modification  of  the  Melan  arch, 
the  ribs  are  built  up  with  angles  for  the  flanges  and  diagonal  lacing 
replaces  the  web,  on  the  theory  that  the  metal  should  be  concentrated 
near  the  extrados  of  the  arch  to  more  effectually  resist  thew  bending 
moments. 


MASONRY  CONSTRUCTION  117 

The  Thacher  type  is  formed  by  omitting  the  web  and  reinforcing 
the  concrete  by  steel  bars  in  pairs  one  above  the  other,  one  near  the 
extrados  and  one  near  the  intrados,  the  steel  being  relied  upon  to 
resist  the  bending  moments  while  the  concrete  is  expected  to  resist 
the  thrust  of  the  arch. 

In  the  Hyatt  arch  that  portion  of  the  steel  bars  or  rods  which  in 
the  Thacher  arch  is  subjected  to  the  greatest  compression  is  omitted. 

In  the  Luter  arch  the  concrete  rib  is  reinforced  by  tension  mem- 
bers passing  from  one  side  of  the  arch  rib  to  the  other. 

In  the  Hennebique  system  an  arch  barrel  or  drum,  four  to  six 
inches  in  diameter,  is  supported  by  ribs  of  concrete  below,  the  concrete 
of  the  drum  being  reinforced  with  steel  rods  placed  near  the  extrados, 
and  that  of  the  ribs  by  steel  rods  near  the  intrados. 

Numerous  forms  of  steel  shapes  are  advocated  for  the  reinforce- 
ment of  concrete  when  employed  for  arches,  retaining  walls,  etc.; 
twisted  bars,  corrugated  bars,  expanded  metal  and  lock  woven  steel 
are  some  of  the  names  applied  to  the  different  shapes. 

The  method  employed  for  constructing  concrete  walls  is  in  brief 
as  follows :  A  wooden  form  is  erected,  consisting  of  slotted  standards 
made  of  6-inch  boards  nailed  together  with  spacing  blocks  between 
them  at  their  ends,  f-inch  bolts  are  used  to  join  the  standards  on 
opposite  sides  of  the  wall.  The  standards  are  for  the  purpose  of 
holding  molding  boards  in  position  while  the  coacrete  is  being  de- 
posited between  them.  These  boards  are  of  dressed  pine  1J  inches 
thick.  After  the  lower  portions  of  the  concrete  has  set  the  boards 
are  removed  and  used  above.  Vertical  rods  of  twisted  or  corrugated 
steel  are  built  in  the  wall  spaced  about  12  inches  apart.  In  some 
cases  level  horizontal  bars  of  steel  are  also  embedded  in  the  walls. 


INDEX 


Page 

Absorptive  power  of  stones,  table 3 

Abutment 96 

definition  of 68 

Activity  of  cement 18 

Adulteration  of  Portland  cement 16 

Age  of  briquette  for  testing 23 

Appearance  of  stone 3 

Arch  bricks 8 

Arch  culverts 112 

Arch  sheeting 97 

Arches 

centering  for 104 

construction  of 104 

description  of 95 

Argillaceous  stones 2 

Arris,  definition  of 63 

Artificial  stones 4 

brick 4 

cement 11 

concrete 33 

Ashlar  backed  with  rubble 82 

Ashlar  masonry. 79 

Asphaltic  concrete 37 

Atmosphere,  effect  of  on  stone 4 

Axed V 75 

Backed,  definition  of 7 63 

Backing 63,  102 

Basket-handle  arch 95 

Bats,  definition  of ". 63 

Batter,  definition  of 63 

Bearing  blocks,  definition  of 63 

Bearing  power  of  soils 54 

Belt  stones,  definition  of 64 

Blocking  course,  definition  of 64 

Boasted 75 

Bond,  definition  of 64 

Bond  of  ashlar  masonry 80 

Box  culverts HI 

Breast  wall,  definition  of 65 

Brick 4 

color  of Q 


120  INDEX 


Page 
Brick 

manufacture  of 6 

rank  of 8 

size  and  weight  of 9 

Brick  arches 103 

Brick  ashlar,  definition  of 65 

Brick  masonry 

impervious  to  water 87 

rules  for  building 84 

Bridge  abutments 106 

Bridge  piers 109 

Briquettes,  testing 24 

Broached 75 

Broken  ashlar 81 

Build,  definition  of 65 

Building  stone,  requisites  for 2 

appearance 3 

cheapness •  •  • 3 

durability 2 

strength. 3 

Bush  hammer 73 

Bush  hammered. 75,  78 

Buttress,  definition  of 65 

Caissons 51 

Calcareous  stones 2 

Camber ..* 97 

Cavil ....  73 

Cement 

activity  of 18 

color  of - 17 

fineness  of x 18 

preservation  of 26 

quick  and  slow  setting ....  19 

soundness  of 20 

testing  of 16 

weight  of 17 

Cement  mortar 29 

Cementing  materials 11 

classification 11 

composition 11 

use , 13 

Centering  for  arches 104 

Cheapness  of  stone 3 

Chemical  classification  of  rocks 2 

argillaceous 2 

calcareous •  2 

silicious • 2 

Cherry  bricks 8 


INDEX  121 


Page 

Chisel 74 

Chiselled 75 

Circular  arch 95 

Clay  puddle 38 

Cleaning  down,  definition  of 65 

Clinker  bricks 8 

Closers,  definition  of 65 

Coefficients  for  retaining  walls,  table 95 

Cofferdams 49 

Color  of  bricks 6 

Color  of  cement 17 

Compass  brick. . .  .  , 8 

Concrete 33 

asphaltic 37 

depositing  under  water 36 

laying 35 

mixing 34 

proportions  of  materials  for 33 

strength  of 33 

weight  of 33 

Concrete  piles , 43 

Concrete  with  steel  beams 48 

Concrete  steel  masonry. 115 

Coping,  definition  of 65 

Corbell,  definition  of 66 

Cornice,  definition  of 66 

Counterfort,  definition  of 66 

Course,  definition  of 66 

Cramps,  definition  of. _ 66 

Crandall 73 

Crandalled 75^  76 

Cribs 50 

Crown  of  arch . 97 

Culverts - HI 

designing  of 112 

Cut  stones ,. .  .  79 

Cutwater,  definition  of 4 . . . , 67 

Deadening 75 

Depositing  concrete  under  water 36 

Designing  culverts 112 

Designing  the  footing 56 

Designing  the  foundation 52 

area  required 54 

bearing  power  of  soils 54 

load  to  be  supported 52 

Discharging  arch 95 

Double-face  hammer 73 

Dowels,  definition  of    . . 67 


122  INDEX 


Page 

Drafted 75 

Drainage 103 

Dressed  work 75 

Dressing  the  stones 72 

Droved 75 

Dry  stone  walls 67 

Durability  of  stone 2 

.Efflorescence 88 

Elliptical  arch 95 

Extrados 97 

Face,  definition  of 67 

Face  brick 8 

Face  hammer 73 

Faces  of  cut  stone,  methods  of  finishing 76 

Facing,  definition  of 67 

Feather-edge  brick 8 

Fine  pointed 76 

Fineness  of  cement 18 

Fire-brick 10 

Flat  arches 103 

Footing,  definition  of 67 

Footings      • 

offsets  of 56 

steel  I-beam 58 

stone 56 

timber ."...' 57 

Formula  for  calculating  thickness  of  retaining  walls 94 

Foundation,  designing 52 

Foundations 39 

artificial 40 

on  clay 40 

on  gravel 39 

on  mud 41 

natural 39 

pile ....,  41 

on  rock 39 

on  sand 40 

in  water 41 

Freezing  of  mortar 31 

Freezing  process 52 

Frost,  effect  of  on  stone 4 

Gauged  work,  definition  of '.  '. 67 

Geological  classification  of  rocks 1 

igneous • 1 

metamorphic .' 1 

sedimentary 1 

Geostatic  arch 95 

Grout  definition  of ;..... 67 


INDEX  123 


Page 

Hammer  dressed 75 

Hand  hammer -74 

Hard  bricks 8 

Hard  kiln-run  brick : .  .  .  8 

Haunches 97 

Header,  definition  of 68 

Heading  joint 97 

Herring  bone 75 

Hollow  cylinders 49 

Hydraulic  limes • 14 

Hydrostatic  arch » 95 

Igneous  rocks 1 

Intrados .  97 

Inverted  arches 96 

Iron  piles 42 

Jamb,  definition  of 69 

Joggle,  definition  of 69 

Joints,  definition  of 68 

Keystone 97 

Kiln-run  brick 8 

Laying  concrete 35 

Limes 13 

hydraulic 14 

poor 14 

rich 13 

Lintel,  definition  of 69 

Load  to  be  supported 52 

Machine-made  brick 7 

Machine  tools 75 

Mallet , 74 

Manufacture  of  brick... 6 

Masonry 

classification  of ' 63 

ashlar 79 

broken  ashlar 81 

rubble \  81 

squared-stone 80 

repair  of 88 

safe  working  loads  for 59 

Masonry  structures 89 

Memoranda  of  cements 25 

Metamorphic  rocks ." 1 

Mixing  concrete 34 

Mortar 27 

freezing  of 31 

proportions 28 

sand  for 28 

uses  of 27 


124  INDEX 


Page 
Mortar 

water  for 29 

Moulded  concrete  piles 43 

Natural  cement 14 

Natural  stones,  classification  of 1 

Nigged 75 

Offsets  of  footings 56 

One-man  stone,  definition  of 69 

Pallets,  definition  of 70 

Parapet  wall,  definition  of 69 

Patent  hammer 74 

Pean  hammer 73 

Pean  hammered 77 

Physical  classification  of  rocks 1 

stratified 1 

unstratified 1 

Pick ! 73 

Picked 75 

Pier. 97 

Pile  driving 44 

Pile  foundations 41 

example  of 55 

Piles 

concrete 43 

iron 42 

moulded  concrete 43 

screw 43 

splicing  of 47 

steel 42 

timber 41 

Pitched , 75 

Pitched-face  masonry,  definition  of 70 

Pitching  chisel 74 

Plain 75 

Plain  arches 96 

Plinth,  definition  of 70 

Plug 74 

Point 74 

Pointed 75 

Pointed  arch. . 96 

Pointing,  definition  of 69 

Polished 75 

Poor  limes 14 

Portland  cement 15 

adulteration 16 

blowing 16 

expansion  and  contraction 16 


INDEX  125 


Page 
Portland  cement 

fineness 15 

overlimed 16 

setting 16 

specific  gravity 15 

tensile  strength 15 

Pozzuolanas 27 

Preservation  of  cements 26 

Preservation  of  stone 4 

Pressed  brick 7 

Pressed  brick  work • 86 

Prison 76 

Puddling 38 

Quarry-faced  masonry,  definition  of 70 

Quick  and  slow  setting  cement . .' 19 

Quoin,  definition  of 70 

Random  tooled 76 

Relieving  arch 96,  104 

Re-pressed  brick 7 

Retaining  walls 92 

coefficients  for 95 

definition  of 71 

failure  of 94 

formula  for  calculating 94 

proportions  of 93 

protection  of 94 

Retempering  mortar 31 

Reveal,  definition  of 71 

Rich  limes 13 

Right  arch , 96 

Rip-rap,  definition  of 71 

Ring  course 97 

Ring  stones 97 

Rise,  definition  of 65,  71 

Rise  of  arch 97 

Rock  faced • 76 

Rocks 1 

chemical  classification 2 

geological  classification ,  .  1 

physical  classification 1 

Roman  cement 27 

Rosendale  cements 14 

Rough  pointed ,  .  76 

Rubble  masonry 81 

Rustic 76 

Safe  working  loads  for  masonry 0 59 

Salmon  bricks 8 

Sampling  cement .  12 


126  INDEX 


Page 

Sand  for  mortar 28 

screening 29 

washing 29 

Sanded  brick 7 

Scabble 76 

Screw  piles 43 

Sedimentary  rocks 1 

Segmental  arch 9G 

Semicircular  arch 96 

Sewer  brick 8 

Sheet  piles 49 

Silicious  stones 2 

Sill,  definition  of 71 

Skew  arch 96 

Skewback 97,  103 

Slag  cements. 26 

Slope-wall  masonry,  definition  of 71 

Soffit 97 

Soft  bricks 8 

Soft-mud  brick 7 

Soundness  of  cement 20 

Spall,  definition  of 71 

Span  of  arch 97 

Spandrel 97 

Spandrel  filling 102 

Specific  gravity  of  Portland  cement. 15 

Splicing  piles 47 

Splitting  chisel 74 

Springer 97 

Springing  of  arch 97 

Square  droved 76 

Squared-stone 78 

Squared-stone  masonry. 80 

Starling,  definition  of 67 

Steel  I-beam  footings : 58 

Steel    piles ? 42 

Stiff-mud  brick ' 7 

Stone  cutting 72 

definitions  of  terms  used  in 75 

tools  used  in 73 

Stone  footings 56 

Stone  masonry,  rules  for  laying  all  classes  of 82 

Stone  paving 71 

Stones 

absorptive  power  of 3 

artificial 4 

brick 4 

cement 11 


INDEX  127 


Page 
Stones 

concrete 33 

preservation  of . , 4 

tests  for 3 

absorptive  power 3 

effect  of  atmosphere. .  - % 4 

effect  of  frost 4 

Stratified  rocks 1 

Strength  of  stone  under  compression 3 

Stretcher,  definition  of 71 

String  course 97 

definition  of ,. 71 

Striped. 76 

Stroked 75 

Structural  materials 1 

Surcharged  walls 93 

Tables 

box  culverts,  dimensions  for 112 

bricks,  size  and  weight  of 9 

cement  and  sand,  amount  required  for  1  cu.  yd.  of  mortar 32 

coefficients  for  retaining  walls 95 

depth  of  keystone  for  semicircular  arches   99 

I-beam  footings,  safe  projection  of 59 

masonry  footing  courses,  safe  offset  for 57 

minimum  thickness  of  abutments  for  arches  of  120° 101 

pile-diving  dimensions 47 

specific  gravity,  weight,  and  resistance  to  crushing  of  brick 10 

specific  gravity,  weight,  and  resistance  to  crushing  of  stones 5 

stones,  absorptive  power  of 3 

tensile  strength  of  cement  mortar 25 

weight  of  masonry ". 53 

Templets,  definition  of 63 

Tensile  strength  of  Portland  cement. 15 

Testing  briquettes 24 

Testing  cements ; 16 

Tests  of  activity 18 

Tests  of  soundness  of  cement 20 

Tests  for  stone 3 

absorptive  power 3 

effect  of  atmosphere 4 

effect  of  frost 4 

Thickness  of  abutments 100 

Thickness  of  arch  at  springing 99 

Timber  footing 57 

Timber  piles 41 

Tooled 76 

Tooth  axe 73,  77 

Tooth  chisel...  74 


128  INDEX 


Page 

Toothed 7(i 

Toothing,  definition  of 71 

Two-men  stone,  definition  of 71 

Unsquared  stones 78 

Unstratified  rocks 1 

Vermiculated  worm  work 76 

Voussoirs 97 

Walls 89 

Water  for  mortar 29 

Waterway,  calculating  area  of .  . 115 

Weep  holes 94 

Weight  of  cement 17 

Wing  walls 112 


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